| Message ID | 20240415142436.2545003-12-roberto.sassu@huaweicloud.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | security: digest_cache LSM | expand |
On Mon Apr 15, 2024 at 5:24 PM EEST, Roberto Sassu wrote: > From: Roberto Sassu <roberto.sassu@huawei.com> > > Register six new LSM hooks, path_truncate, file_release, inode_unlink, > inode_rename, inode_post_setxattr and inode_post_removexattr, to monitor > digest lists/directory modifications. > > If an action affects a digest list or the parent directory, the new LSM > hook implementations call digest_cache_reset_owner() to set the RESET bit > (if unset) on the digest cache pointed to by dig_owner in the inode > security blob. This will cause next calls to digest_cache_get() and > digest_cache_create() to respectively put and clear dig_user and dig_owner, > and request a new digest cache. > > If an action affects a file using a digest cache, the new LSM hook > implementations call digest_cache_reset_user() to set the RESET_USER bit > (if unset) on the digest cache pointed to by dig_user in the inode security > blob. This will cause next calls to digest_cache_get() to put and clear > dig_user, and retrieve the digest cache again. > > That does not affect other users of the old digest cache, since that one > remains valid as long as the reference count is greater than zero. However, > they will be notified in a subsequent patch about the reset, so that they > can eventually request a new digest cache. > > Recreating a file digest cache means reading the digest list again and > extracting the digests. Recreating a directory digest cache, instead, does > not mean recreating the digest cache for directory entries, since those > digest caches are likely already stored in the inode security blob. It > would happen however for new files. > > Dig_owner reset for file digest caches is done on path_truncate, when a > digest list is truncated (there is no inode_truncate, file_truncate does > not catch operations through the truncate() system call), file_release, > when a digest list opened for write is being closed, inode_unlink, when a > digest list is removed, and inode_rename when a digest list is renamed. > > Dig_owner reset for directory digest caches is done on file_release, when a > new digest list is written in the digest list directory, on inode_unlink, > when a digest list is deleted from that directory, and finally on > inode_rename, when a digest list is moved to/from that directory. > > Dig_user reset is always done on inode_post_setxattr and > inode_post_removexattr, when the security.digest_list xattr is respectively > set or removed from a file using a digest cache. > > With the exception of file_release, which will always be executed (cannot > be denied), and inode_post_setxattr and inode_post_removexattr, which are > executed after the actual operation, the other LSM hooks are not optimal, > since the digest_cache LSM does not know whether or not the operation will > be allowed also by other LSMs. If the operation is denied, the digest_cache > LSM would do an unnecessary reset. > > Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com> > --- > security/digest_cache/Kconfig | 1 + > security/digest_cache/Makefile | 3 +- > security/digest_cache/dir.c | 6 + > security/digest_cache/internal.h | 14 +++ > security/digest_cache/main.c | 19 +++ > security/digest_cache/reset.c | 197 +++++++++++++++++++++++++++++++ > 6 files changed, 239 insertions(+), 1 deletion(-) > create mode 100644 security/digest_cache/reset.c > > diff --git a/security/digest_cache/Kconfig b/security/digest_cache/Kconfig > index cb4fa44e8f2a..54ba3a585073 100644 > --- a/security/digest_cache/Kconfig > +++ b/security/digest_cache/Kconfig > @@ -2,6 +2,7 @@ > config SECURITY_DIGEST_CACHE > bool "Digest_cache LSM" > select TLV_PARSER > + select SECURITY_PATH > default n > help > This option enables an LSM maintaining a cache of digests > diff --git a/security/digest_cache/Makefile b/security/digest_cache/Makefile > index e417da0383ab..3d5e600a2c45 100644 > --- a/security/digest_cache/Makefile > +++ b/security/digest_cache/Makefile > @@ -4,7 +4,8 @@ > > obj-$(CONFIG_SECURITY_DIGEST_CACHE) += digest_cache.o > > -digest_cache-y := main.o secfs.o htable.o populate.o modsig.o verif.o dir.o > +digest_cache-y := main.o secfs.o htable.o populate.o modsig.o verif.o dir.o \ > + reset.o > > digest_cache-y += parsers/tlv.o > digest_cache-y += parsers/rpm.o > diff --git a/security/digest_cache/dir.c b/security/digest_cache/dir.c > index a7d203c15386..937177660242 100644 > --- a/security/digest_cache/dir.c > +++ b/security/digest_cache/dir.c > @@ -148,6 +148,12 @@ digest_cache_dir_lookup_digest(struct dentry *dentry, > > list_for_each_entry(dir_entry, &digest_cache->dir_entries, list) { > mutex_lock(&dir_entry->digest_cache_mutex); > + if (dir_entry->digest_cache && > + test_bit(RESET, &dir_entry->digest_cache->flags)) { > + digest_cache_put(dir_entry->digest_cache); > + dir_entry->digest_cache = NULL; > + } > + > if (!dir_entry->digest_cache) { > cache = digest_cache_create(dentry, digest_list_path, > digest_cache->path_str, > diff --git a/security/digest_cache/internal.h b/security/digest_cache/internal.h > index c13b35f6b2c0..c816929c4743 100644 > --- a/security/digest_cache/internal.h > +++ b/security/digest_cache/internal.h > @@ -18,6 +18,8 @@ > #define INVALID 1 /* Digest cache marked as invalid. */ > #define IS_DIR 2 /* Digest cache created from dir. */ > #define DIR_PREFETCH 3 /* Prefetching requested for dir. */ > +#define RESET 4 /* Digest cache to be recreated. */ > +#define RESET_USER 5 /* Dig_user pointer to be released. */ > > /** > * struct readdir_callback - Structure to store information for dir iteration > @@ -247,4 +249,16 @@ digest_cache_dir_lookup_filename(struct dentry *dentry, > char *filename); > void digest_cache_dir_free(struct digest_cache *digest_cache); > > +/* reset.c */ > +int digest_cache_path_truncate(const struct path *path); > +void digest_cache_file_release(struct file *file); > +int digest_cache_inode_unlink(struct inode *dir, struct dentry *dentry); > +int digest_cache_inode_rename(struct inode *old_dir, struct dentry *old_dentry, > + struct inode *new_dir, struct dentry *new_dentry); > +void digest_cache_inode_post_setxattr(struct dentry *dentry, const char *name, > + const void *value, size_t size, > + int flags); > +void digest_cache_inode_post_removexattr(struct dentry *dentry, > + const char *name); > + > #endif /* _DIGEST_CACHE_INTERNAL_H */ > diff --git a/security/digest_cache/main.c b/security/digest_cache/main.c > index a5616fd07c1d..ce3518a33c80 100644 > --- a/security/digest_cache/main.c > +++ b/security/digest_cache/main.c > @@ -169,6 +169,11 @@ struct digest_cache *digest_cache_create(struct dentry *dentry, > > /* Serialize check and assignment of dig_owner. */ > mutex_lock(&dig_sec->dig_owner_mutex); > + if (dig_sec->dig_owner && test_bit(RESET, &dig_sec->dig_owner->flags)) { > + digest_cache_put(dig_sec->dig_owner); > + dig_sec->dig_owner = NULL; > + } > + > if (dig_sec->dig_owner) { > /* Increment ref. count for reference returned to the caller. */ > digest_cache = digest_cache_ref(dig_sec->dig_owner); > @@ -403,6 +408,13 @@ struct digest_cache *digest_cache_get(struct dentry *dentry) > > /* Serialize accesses to inode for which the digest cache is used. */ > mutex_lock(&dig_sec->dig_user_mutex); > + if (dig_sec->dig_user && > + (test_bit(RESET, &dig_sec->dig_user->flags) || > + test_bit(RESET_USER, &dig_sec->dig_user->flags))) { > + digest_cache_put(dig_sec->dig_user); > + dig_sec->dig_user = NULL; > + } > + > if (!dig_sec->dig_user) { > down_read(&default_path_sem); > /* Consume extra reference from digest_cache_create(). */ > @@ -491,6 +503,13 @@ static void digest_cache_inode_free_security(struct inode *inode) > static struct security_hook_list digest_cache_hooks[] __ro_after_init = { > LSM_HOOK_INIT(inode_alloc_security, digest_cache_inode_alloc_security), > LSM_HOOK_INIT(inode_free_security, digest_cache_inode_free_security), > + LSM_HOOK_INIT(path_truncate, digest_cache_path_truncate), > + LSM_HOOK_INIT(file_release, digest_cache_file_release), > + LSM_HOOK_INIT(inode_unlink, digest_cache_inode_unlink), > + LSM_HOOK_INIT(inode_rename, digest_cache_inode_rename), > + LSM_HOOK_INIT(inode_post_setxattr, digest_cache_inode_post_setxattr), > + LSM_HOOK_INIT(inode_post_removexattr, > + digest_cache_inode_post_removexattr), > }; > > /** > diff --git a/security/digest_cache/reset.c b/security/digest_cache/reset.c > new file mode 100644 > index 000000000000..e07222b0e0e8 > --- /dev/null > +++ b/security/digest_cache/reset.c > @@ -0,0 +1,197 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * Copyright (C) 2023-2024 Huawei Technologies Duesseldorf GmbH > + * > + * Author: Roberto Sassu <roberto.sassu@huawei.com> > + * > + * Reset digest cache on digest lists/directory modifications. > + */ > + > +#define pr_fmt(fmt) "DIGEST CACHE: "fmt > +#include "internal.h" > + > +/** > + * digest_cache_reset_owner - Reset dig_owner > + * @inode: Inode of the digest list/directory containing the digest list > + * @reason: Reason for reset > + * > + * This function sets the RESET bit of the digest cache pointed to by dig_owner > + * (if unset), so that digest_cache_get() and digest_cache_create() respectively > + * release and clear dig_user and dig_owner in the inode security blob. This > + * causes new callers of digest_cache_get() to get a new digest cache. > + */ > +static void digest_cache_reset_owner(struct inode *inode, const char *reason) > +{ > + struct digest_cache_security *dig_sec; > + > + dig_sec = digest_cache_get_security(inode); > + if (unlikely(!dig_sec)) > + return; > + > + mutex_lock(&dig_sec->dig_owner_mutex); > + if (dig_sec->dig_owner && > + !test_and_set_bit(RESET, &dig_sec->dig_owner->flags)) > + pr_debug("Resetting %s (dig_owner), reason: %s\n", > + dig_sec->dig_owner->path_str, reason); > + mutex_unlock(&dig_sec->dig_owner_mutex); > +} > + > +/** > + * digest_cache_reset_user - Reset dig_user > + * @inode: Inode of the file using the digest cache > + * @reason: Reason for reset > + * > + * This function sets the RESET_USER bit (if unset), so that digest_cache_get() > + * clears the dig_user pointer in the inode security blob and determines again > + * the digest list inode to get a digest cache from. > + */ > +static void digest_cache_reset_user(struct inode *inode, const char *reason) > +{ > + struct digest_cache_security *dig_sec; > + > + dig_sec = digest_cache_get_security(inode); > + if (unlikely(!dig_sec)) > + return; > + > + mutex_lock(&dig_sec->dig_user_mutex); > + if (dig_sec->dig_user && > + !test_and_set_bit(RESET_USER, &dig_sec->dig_user->flags)) > + pr_debug("Resetting %s (dig_user), reason: %s\n", > + dig_sec->dig_user->path_str, reason); > + mutex_unlock(&dig_sec->dig_user_mutex); > +} > + > +/** > + * digest_cache_path_truncate - A file is being truncated > + * @path: File path > + * > + * This function is called when a file is being truncated. If the inode is a > + * digest list, it resets the inode dig_owner, to force rebuilding the digest > + * cache. > + * > + * Return: Zero. > + */ > +int digest_cache_path_truncate(const struct path *path) > +{ > + struct inode *inode = d_backing_inode(path->dentry); > + > + if (!S_ISREG(inode->i_mode)) > + return 0; > + > + digest_cache_reset_owner(inode, "file_truncate"); > + return 0; > +} > + > +/** > + * digest_cache_file_release - Last reference of a file desc is being released > + * @file: File descriptor > + * > + * This function is called when the last reference of a file descriptor is > + * being released. If the inode is a regular file and was opened for write, or > + * the parent inode is the digest list directory and the file was created, it > + * resets the inode dig_owner, to force rebuilding the digest cache. > + */ > +void digest_cache_file_release(struct file *file) > +{ > + struct inode *dir = d_backing_inode(file_dentry(file)->d_parent); > + > + if (!S_ISREG(file_inode(file)->i_mode) || !(file->f_mode & FMODE_WRITE)) > + return; > + > + digest_cache_reset_owner(file_inode(file), "file_file_release"); > + if (file->f_mode & FMODE_CREATED) > + digest_cache_reset_owner(dir, "dir_file_release"); > +} > + > +/** > + * digest_cache_inode_unlink - An inode is being removed > + * @dir: Inode of the affected directory > + * @dentry: Dentry of the inode being removed > + * > + * This function is called when an existing inode is being removed. If the > + * inode is a digest list, or the parent inode is the digest list directory and > + * the inode is a regular file, it resets the affected inode dig_owner, to force > + * rebuilding the digest cache. > + * > + * Return: Zero. > + */ > +int digest_cache_inode_unlink(struct inode *dir, struct dentry *dentry) > +{ > + struct inode *inode = d_backing_inode(dentry); > + > + if (!S_ISREG(inode->i_mode)) > + return 0; > + > + digest_cache_reset_owner(inode, "file_unlink"); > + digest_cache_reset_owner(dir, "dir_unlink"); > + return 0; > +} > + > +/** > + * digest_cache_inode_rename - An inode is being renamed > + * @old_dir: Inode of the directory containing the inode being renamed > + * @old_dentry: Dentry of the inode being renamed > + * @new_dir: Directory where the inode will be placed into > + * @new_dentry: Dentry of the inode after being renamed > + * > + * This function is called when an existing inode is being moved from a > + * directory to another (rename). If the inode is a digest list, or that inode > + * is moved from/to the digest list directory, it resets the affected inode > + * dig_owner, to force rebuilding the digest cache. > + * > + * Return: Zero. > + */ > +int digest_cache_inode_rename(struct inode *old_dir, struct dentry *old_dentry, > + struct inode *new_dir, struct dentry *new_dentry) > +{ > + struct inode *old_inode = d_backing_inode(old_dentry); > + > + if (!S_ISREG(old_inode->i_mode)) > + return 0; > + > + digest_cache_reset_owner(old_inode, "file_rename"); > + digest_cache_reset_owner(old_dir, "dir_rename_from"); > + digest_cache_reset_owner(new_dir, "dir_rename_to"); > + return 0; > +} > + > +/** > + * digest_cache_inode_post_setxattr() - An xattr was set > + * @dentry: file > + * @name: xattr name > + * @value: xattr value > + * @size: size of xattr value > + * @flags: flags > + * > + * This function is called after an xattr was set on an existing inode. If the > + * inode points to a digest cache and the xattr set is security.digest_list, it > + * resets dig_user in the inode security blob, to force retrieving a fresh > + * digest cache. > + */ > +void digest_cache_inode_post_setxattr(struct dentry *dentry, const char *name, > + const void *value, size_t size, int flags) > +{ > + if (strcmp(name, XATTR_NAME_DIGEST_LIST)) > + return; > + > + digest_cache_reset_user(d_backing_inode(dentry), "file_setxattr"); > +} > + > +/** > + * digest_cache_inode_post_removexattr() - An xattr was removed > + * @dentry: file > + * @name: xattr name > + * > + * This function is called after an xattr was removed from an existing inode. > + * If the inode points to a digest cache and the xattr removed is > + * security.digest_list, it resets dig_user in the inode security blob, to > + * force retrieving a fresh digest cache. > + */ > +void digest_cache_inode_post_removexattr(struct dentry *dentry, > + const char *name) nit: void digest_cache_inode_post_removexattr(struct dentry *dentry, const char *name) would be fine too > +{ > + if (strcmp(name, XATTR_NAME_DIGEST_LIST)) > + return; > + > + digest_cache_reset_user(d_backing_inode(dentry), "file_removexattr"); > +} BR, Jarkko
On 4/15/2024 9:44 PM, Jarkko Sakkinen wrote: > On Mon Apr 15, 2024 at 5:24 PM EEST, Roberto Sassu wrote: >> From: Roberto Sassu <roberto.sassu@huawei.com> >> >> Register six new LSM hooks, path_truncate, file_release, inode_unlink, >> inode_rename, inode_post_setxattr and inode_post_removexattr, to monitor >> digest lists/directory modifications. >> >> If an action affects a digest list or the parent directory, the new LSM >> hook implementations call digest_cache_reset_owner() to set the RESET bit >> (if unset) on the digest cache pointed to by dig_owner in the inode >> security blob. This will cause next calls to digest_cache_get() and >> digest_cache_create() to respectively put and clear dig_user and dig_owner, >> and request a new digest cache. >> >> If an action affects a file using a digest cache, the new LSM hook >> implementations call digest_cache_reset_user() to set the RESET_USER bit >> (if unset) on the digest cache pointed to by dig_user in the inode security >> blob. This will cause next calls to digest_cache_get() to put and clear >> dig_user, and retrieve the digest cache again. >> >> That does not affect other users of the old digest cache, since that one >> remains valid as long as the reference count is greater than zero. However, >> they will be notified in a subsequent patch about the reset, so that they >> can eventually request a new digest cache. >> >> Recreating a file digest cache means reading the digest list again and >> extracting the digests. Recreating a directory digest cache, instead, does >> not mean recreating the digest cache for directory entries, since those >> digest caches are likely already stored in the inode security blob. It >> would happen however for new files. >> >> Dig_owner reset for file digest caches is done on path_truncate, when a >> digest list is truncated (there is no inode_truncate, file_truncate does >> not catch operations through the truncate() system call), file_release, >> when a digest list opened for write is being closed, inode_unlink, when a >> digest list is removed, and inode_rename when a digest list is renamed. >> >> Dig_owner reset for directory digest caches is done on file_release, when a >> new digest list is written in the digest list directory, on inode_unlink, >> when a digest list is deleted from that directory, and finally on >> inode_rename, when a digest list is moved to/from that directory. >> >> Dig_user reset is always done on inode_post_setxattr and >> inode_post_removexattr, when the security.digest_list xattr is respectively >> set or removed from a file using a digest cache. >> >> With the exception of file_release, which will always be executed (cannot >> be denied), and inode_post_setxattr and inode_post_removexattr, which are >> executed after the actual operation, the other LSM hooks are not optimal, >> since the digest_cache LSM does not know whether or not the operation will >> be allowed also by other LSMs. If the operation is denied, the digest_cache >> LSM would do an unnecessary reset. >> >> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com> >> --- >> security/digest_cache/Kconfig | 1 + >> security/digest_cache/Makefile | 3 +- >> security/digest_cache/dir.c | 6 + >> security/digest_cache/internal.h | 14 +++ >> security/digest_cache/main.c | 19 +++ >> security/digest_cache/reset.c | 197 +++++++++++++++++++++++++++++++ >> 6 files changed, 239 insertions(+), 1 deletion(-) >> create mode 100644 security/digest_cache/reset.c >> >> diff --git a/security/digest_cache/Kconfig b/security/digest_cache/Kconfig >> index cb4fa44e8f2a..54ba3a585073 100644 >> --- a/security/digest_cache/Kconfig >> +++ b/security/digest_cache/Kconfig >> @@ -2,6 +2,7 @@ >> config SECURITY_DIGEST_CACHE >> bool "Digest_cache LSM" >> select TLV_PARSER >> + select SECURITY_PATH >> default n >> help >> This option enables an LSM maintaining a cache of digests >> diff --git a/security/digest_cache/Makefile b/security/digest_cache/Makefile >> index e417da0383ab..3d5e600a2c45 100644 >> --- a/security/digest_cache/Makefile >> +++ b/security/digest_cache/Makefile >> @@ -4,7 +4,8 @@ >> >> obj-$(CONFIG_SECURITY_DIGEST_CACHE) += digest_cache.o >> >> -digest_cache-y := main.o secfs.o htable.o populate.o modsig.o verif.o dir.o >> +digest_cache-y := main.o secfs.o htable.o populate.o modsig.o verif.o dir.o \ >> + reset.o >> >> digest_cache-y += parsers/tlv.o >> digest_cache-y += parsers/rpm.o >> diff --git a/security/digest_cache/dir.c b/security/digest_cache/dir.c >> index a7d203c15386..937177660242 100644 >> --- a/security/digest_cache/dir.c >> +++ b/security/digest_cache/dir.c >> @@ -148,6 +148,12 @@ digest_cache_dir_lookup_digest(struct dentry *dentry, >> >> list_for_each_entry(dir_entry, &digest_cache->dir_entries, list) { >> mutex_lock(&dir_entry->digest_cache_mutex); >> + if (dir_entry->digest_cache && >> + test_bit(RESET, &dir_entry->digest_cache->flags)) { >> + digest_cache_put(dir_entry->digest_cache); >> + dir_entry->digest_cache = NULL; >> + } >> + >> if (!dir_entry->digest_cache) { >> cache = digest_cache_create(dentry, digest_list_path, >> digest_cache->path_str, >> diff --git a/security/digest_cache/internal.h b/security/digest_cache/internal.h >> index c13b35f6b2c0..c816929c4743 100644 >> --- a/security/digest_cache/internal.h >> +++ b/security/digest_cache/internal.h >> @@ -18,6 +18,8 @@ >> #define INVALID 1 /* Digest cache marked as invalid. */ >> #define IS_DIR 2 /* Digest cache created from dir. */ >> #define DIR_PREFETCH 3 /* Prefetching requested for dir. */ >> +#define RESET 4 /* Digest cache to be recreated. */ >> +#define RESET_USER 5 /* Dig_user pointer to be released. */ >> >> /** >> * struct readdir_callback - Structure to store information for dir iteration >> @@ -247,4 +249,16 @@ digest_cache_dir_lookup_filename(struct dentry *dentry, >> char *filename); >> void digest_cache_dir_free(struct digest_cache *digest_cache); >> >> +/* reset.c */ >> +int digest_cache_path_truncate(const struct path *path); >> +void digest_cache_file_release(struct file *file); >> +int digest_cache_inode_unlink(struct inode *dir, struct dentry *dentry); >> +int digest_cache_inode_rename(struct inode *old_dir, struct dentry *old_dentry, >> + struct inode *new_dir, struct dentry *new_dentry); >> +void digest_cache_inode_post_setxattr(struct dentry *dentry, const char *name, >> + const void *value, size_t size, >> + int flags); >> +void digest_cache_inode_post_removexattr(struct dentry *dentry, >> + const char *name); >> + >> #endif /* _DIGEST_CACHE_INTERNAL_H */ >> diff --git a/security/digest_cache/main.c b/security/digest_cache/main.c >> index a5616fd07c1d..ce3518a33c80 100644 >> --- a/security/digest_cache/main.c >> +++ b/security/digest_cache/main.c >> @@ -169,6 +169,11 @@ struct digest_cache *digest_cache_create(struct dentry *dentry, >> >> /* Serialize check and assignment of dig_owner. */ >> mutex_lock(&dig_sec->dig_owner_mutex); >> + if (dig_sec->dig_owner && test_bit(RESET, &dig_sec->dig_owner->flags)) { >> + digest_cache_put(dig_sec->dig_owner); >> + dig_sec->dig_owner = NULL; >> + } >> + >> if (dig_sec->dig_owner) { >> /* Increment ref. count for reference returned to the caller. */ >> digest_cache = digest_cache_ref(dig_sec->dig_owner); >> @@ -403,6 +408,13 @@ struct digest_cache *digest_cache_get(struct dentry *dentry) >> >> /* Serialize accesses to inode for which the digest cache is used. */ >> mutex_lock(&dig_sec->dig_user_mutex); >> + if (dig_sec->dig_user && >> + (test_bit(RESET, &dig_sec->dig_user->flags) || >> + test_bit(RESET_USER, &dig_sec->dig_user->flags))) { >> + digest_cache_put(dig_sec->dig_user); >> + dig_sec->dig_user = NULL; >> + } >> + >> if (!dig_sec->dig_user) { >> down_read(&default_path_sem); >> /* Consume extra reference from digest_cache_create(). */ >> @@ -491,6 +503,13 @@ static void digest_cache_inode_free_security(struct inode *inode) >> static struct security_hook_list digest_cache_hooks[] __ro_after_init = { >> LSM_HOOK_INIT(inode_alloc_security, digest_cache_inode_alloc_security), >> LSM_HOOK_INIT(inode_free_security, digest_cache_inode_free_security), >> + LSM_HOOK_INIT(path_truncate, digest_cache_path_truncate), >> + LSM_HOOK_INIT(file_release, digest_cache_file_release), >> + LSM_HOOK_INIT(inode_unlink, digest_cache_inode_unlink), >> + LSM_HOOK_INIT(inode_rename, digest_cache_inode_rename), >> + LSM_HOOK_INIT(inode_post_setxattr, digest_cache_inode_post_setxattr), >> + LSM_HOOK_INIT(inode_post_removexattr, >> + digest_cache_inode_post_removexattr), >> }; >> >> /** >> diff --git a/security/digest_cache/reset.c b/security/digest_cache/reset.c >> new file mode 100644 >> index 000000000000..e07222b0e0e8 >> --- /dev/null >> +++ b/security/digest_cache/reset.c >> @@ -0,0 +1,197 @@ >> +// SPDX-License-Identifier: GPL-2.0 >> +/* >> + * Copyright (C) 2023-2024 Huawei Technologies Duesseldorf GmbH >> + * >> + * Author: Roberto Sassu <roberto.sassu@huawei.com> >> + * >> + * Reset digest cache on digest lists/directory modifications. >> + */ >> + >> +#define pr_fmt(fmt) "DIGEST CACHE: "fmt >> +#include "internal.h" >> + >> +/** >> + * digest_cache_reset_owner - Reset dig_owner >> + * @inode: Inode of the digest list/directory containing the digest list >> + * @reason: Reason for reset >> + * >> + * This function sets the RESET bit of the digest cache pointed to by dig_owner >> + * (if unset), so that digest_cache_get() and digest_cache_create() respectively >> + * release and clear dig_user and dig_owner in the inode security blob. This >> + * causes new callers of digest_cache_get() to get a new digest cache. >> + */ >> +static void digest_cache_reset_owner(struct inode *inode, const char *reason) >> +{ >> + struct digest_cache_security *dig_sec; >> + >> + dig_sec = digest_cache_get_security(inode); >> + if (unlikely(!dig_sec)) >> + return; >> + >> + mutex_lock(&dig_sec->dig_owner_mutex); >> + if (dig_sec->dig_owner && >> + !test_and_set_bit(RESET, &dig_sec->dig_owner->flags)) >> + pr_debug("Resetting %s (dig_owner), reason: %s\n", >> + dig_sec->dig_owner->path_str, reason); >> + mutex_unlock(&dig_sec->dig_owner_mutex); >> +} >> + >> +/** >> + * digest_cache_reset_user - Reset dig_user >> + * @inode: Inode of the file using the digest cache >> + * @reason: Reason for reset >> + * >> + * This function sets the RESET_USER bit (if unset), so that digest_cache_get() >> + * clears the dig_user pointer in the inode security blob and determines again >> + * the digest list inode to get a digest cache from. >> + */ >> +static void digest_cache_reset_user(struct inode *inode, const char *reason) >> +{ >> + struct digest_cache_security *dig_sec; >> + >> + dig_sec = digest_cache_get_security(inode); >> + if (unlikely(!dig_sec)) >> + return; >> + >> + mutex_lock(&dig_sec->dig_user_mutex); >> + if (dig_sec->dig_user && >> + !test_and_set_bit(RESET_USER, &dig_sec->dig_user->flags)) >> + pr_debug("Resetting %s (dig_user), reason: %s\n", >> + dig_sec->dig_user->path_str, reason); >> + mutex_unlock(&dig_sec->dig_user_mutex); >> +} >> + >> +/** >> + * digest_cache_path_truncate - A file is being truncated >> + * @path: File path >> + * >> + * This function is called when a file is being truncated. If the inode is a >> + * digest list, it resets the inode dig_owner, to force rebuilding the digest >> + * cache. >> + * >> + * Return: Zero. >> + */ >> +int digest_cache_path_truncate(const struct path *path) >> +{ >> + struct inode *inode = d_backing_inode(path->dentry); >> + >> + if (!S_ISREG(inode->i_mode)) >> + return 0; >> + >> + digest_cache_reset_owner(inode, "file_truncate"); >> + return 0; >> +} >> + >> +/** >> + * digest_cache_file_release - Last reference of a file desc is being released >> + * @file: File descriptor >> + * >> + * This function is called when the last reference of a file descriptor is >> + * being released. If the inode is a regular file and was opened for write, or >> + * the parent inode is the digest list directory and the file was created, it >> + * resets the inode dig_owner, to force rebuilding the digest cache. >> + */ >> +void digest_cache_file_release(struct file *file) >> +{ >> + struct inode *dir = d_backing_inode(file_dentry(file)->d_parent); >> + >> + if (!S_ISREG(file_inode(file)->i_mode) || !(file->f_mode & FMODE_WRITE)) >> + return; >> + >> + digest_cache_reset_owner(file_inode(file), "file_file_release"); >> + if (file->f_mode & FMODE_CREATED) >> + digest_cache_reset_owner(dir, "dir_file_release"); >> +} >> + >> +/** >> + * digest_cache_inode_unlink - An inode is being removed >> + * @dir: Inode of the affected directory >> + * @dentry: Dentry of the inode being removed >> + * >> + * This function is called when an existing inode is being removed. If the >> + * inode is a digest list, or the parent inode is the digest list directory and >> + * the inode is a regular file, it resets the affected inode dig_owner, to force >> + * rebuilding the digest cache. >> + * >> + * Return: Zero. >> + */ >> +int digest_cache_inode_unlink(struct inode *dir, struct dentry *dentry) >> +{ >> + struct inode *inode = d_backing_inode(dentry); >> + >> + if (!S_ISREG(inode->i_mode)) >> + return 0; >> + >> + digest_cache_reset_owner(inode, "file_unlink"); >> + digest_cache_reset_owner(dir, "dir_unlink"); >> + return 0; >> +} >> + >> +/** >> + * digest_cache_inode_rename - An inode is being renamed >> + * @old_dir: Inode of the directory containing the inode being renamed >> + * @old_dentry: Dentry of the inode being renamed >> + * @new_dir: Directory where the inode will be placed into >> + * @new_dentry: Dentry of the inode after being renamed >> + * >> + * This function is called when an existing inode is being moved from a >> + * directory to another (rename). If the inode is a digest list, or that inode >> + * is moved from/to the digest list directory, it resets the affected inode >> + * dig_owner, to force rebuilding the digest cache. >> + * >> + * Return: Zero. >> + */ >> +int digest_cache_inode_rename(struct inode *old_dir, struct dentry *old_dentry, >> + struct inode *new_dir, struct dentry *new_dentry) >> +{ >> + struct inode *old_inode = d_backing_inode(old_dentry); >> + >> + if (!S_ISREG(old_inode->i_mode)) >> + return 0; >> + >> + digest_cache_reset_owner(old_inode, "file_rename"); >> + digest_cache_reset_owner(old_dir, "dir_rename_from"); >> + digest_cache_reset_owner(new_dir, "dir_rename_to"); >> + return 0; >> +} >> + >> +/** >> + * digest_cache_inode_post_setxattr() - An xattr was set >> + * @dentry: file >> + * @name: xattr name >> + * @value: xattr value >> + * @size: size of xattr value >> + * @flags: flags >> + * >> + * This function is called after an xattr was set on an existing inode. If the >> + * inode points to a digest cache and the xattr set is security.digest_list, it >> + * resets dig_user in the inode security blob, to force retrieving a fresh >> + * digest cache. >> + */ >> +void digest_cache_inode_post_setxattr(struct dentry *dentry, const char *name, >> + const void *value, size_t size, int flags) >> +{ >> + if (strcmp(name, XATTR_NAME_DIGEST_LIST)) >> + return; >> + >> + digest_cache_reset_user(d_backing_inode(dentry), "file_setxattr"); >> +} >> + >> +/** >> + * digest_cache_inode_post_removexattr() - An xattr was removed >> + * @dentry: file >> + * @name: xattr name >> + * >> + * This function is called after an xattr was removed from an existing inode. >> + * If the inode points to a digest cache and the xattr removed is >> + * security.digest_list, it resets dig_user in the inode security blob, to >> + * force retrieving a fresh digest cache. >> + */ >> +void digest_cache_inode_post_removexattr(struct dentry *dentry, >> + const char *name) > > nit: > > void digest_cache_inode_post_removexattr(struct dentry *dentry, const char *name) > > would be fine too I still prefer to stay within 80 characters. Thanks Roberto >> +{ >> + if (strcmp(name, XATTR_NAME_DIGEST_LIST)) >> + return; >> + >> + digest_cache_reset_user(d_backing_inode(dentry), "file_removexattr"); >> +} > > > BR, Jarkko
diff --git a/security/digest_cache/Kconfig b/security/digest_cache/Kconfig index cb4fa44e8f2a..54ba3a585073 100644 --- a/security/digest_cache/Kconfig +++ b/security/digest_cache/Kconfig @@ -2,6 +2,7 @@ config SECURITY_DIGEST_CACHE bool "Digest_cache LSM" select TLV_PARSER + select SECURITY_PATH default n help This option enables an LSM maintaining a cache of digests diff --git a/security/digest_cache/Makefile b/security/digest_cache/Makefile index e417da0383ab..3d5e600a2c45 100644 --- a/security/digest_cache/Makefile +++ b/security/digest_cache/Makefile @@ -4,7 +4,8 @@ obj-$(CONFIG_SECURITY_DIGEST_CACHE) += digest_cache.o -digest_cache-y := main.o secfs.o htable.o populate.o modsig.o verif.o dir.o +digest_cache-y := main.o secfs.o htable.o populate.o modsig.o verif.o dir.o \ + reset.o digest_cache-y += parsers/tlv.o digest_cache-y += parsers/rpm.o diff --git a/security/digest_cache/dir.c b/security/digest_cache/dir.c index a7d203c15386..937177660242 100644 --- a/security/digest_cache/dir.c +++ b/security/digest_cache/dir.c @@ -148,6 +148,12 @@ digest_cache_dir_lookup_digest(struct dentry *dentry, list_for_each_entry(dir_entry, &digest_cache->dir_entries, list) { mutex_lock(&dir_entry->digest_cache_mutex); + if (dir_entry->digest_cache && + test_bit(RESET, &dir_entry->digest_cache->flags)) { + digest_cache_put(dir_entry->digest_cache); + dir_entry->digest_cache = NULL; + } + if (!dir_entry->digest_cache) { cache = digest_cache_create(dentry, digest_list_path, digest_cache->path_str, diff --git a/security/digest_cache/internal.h b/security/digest_cache/internal.h index c13b35f6b2c0..c816929c4743 100644 --- a/security/digest_cache/internal.h +++ b/security/digest_cache/internal.h @@ -18,6 +18,8 @@ #define INVALID 1 /* Digest cache marked as invalid. */ #define IS_DIR 2 /* Digest cache created from dir. */ #define DIR_PREFETCH 3 /* Prefetching requested for dir. */ +#define RESET 4 /* Digest cache to be recreated. */ +#define RESET_USER 5 /* Dig_user pointer to be released. */ /** * struct readdir_callback - Structure to store information for dir iteration @@ -247,4 +249,16 @@ digest_cache_dir_lookup_filename(struct dentry *dentry, char *filename); void digest_cache_dir_free(struct digest_cache *digest_cache); +/* reset.c */ +int digest_cache_path_truncate(const struct path *path); +void digest_cache_file_release(struct file *file); +int digest_cache_inode_unlink(struct inode *dir, struct dentry *dentry); +int digest_cache_inode_rename(struct inode *old_dir, struct dentry *old_dentry, + struct inode *new_dir, struct dentry *new_dentry); +void digest_cache_inode_post_setxattr(struct dentry *dentry, const char *name, + const void *value, size_t size, + int flags); +void digest_cache_inode_post_removexattr(struct dentry *dentry, + const char *name); + #endif /* _DIGEST_CACHE_INTERNAL_H */ diff --git a/security/digest_cache/main.c b/security/digest_cache/main.c index a5616fd07c1d..ce3518a33c80 100644 --- a/security/digest_cache/main.c +++ b/security/digest_cache/main.c @@ -169,6 +169,11 @@ struct digest_cache *digest_cache_create(struct dentry *dentry, /* Serialize check and assignment of dig_owner. */ mutex_lock(&dig_sec->dig_owner_mutex); + if (dig_sec->dig_owner && test_bit(RESET, &dig_sec->dig_owner->flags)) { + digest_cache_put(dig_sec->dig_owner); + dig_sec->dig_owner = NULL; + } + if (dig_sec->dig_owner) { /* Increment ref. count for reference returned to the caller. */ digest_cache = digest_cache_ref(dig_sec->dig_owner); @@ -403,6 +408,13 @@ struct digest_cache *digest_cache_get(struct dentry *dentry) /* Serialize accesses to inode for which the digest cache is used. */ mutex_lock(&dig_sec->dig_user_mutex); + if (dig_sec->dig_user && + (test_bit(RESET, &dig_sec->dig_user->flags) || + test_bit(RESET_USER, &dig_sec->dig_user->flags))) { + digest_cache_put(dig_sec->dig_user); + dig_sec->dig_user = NULL; + } + if (!dig_sec->dig_user) { down_read(&default_path_sem); /* Consume extra reference from digest_cache_create(). */ @@ -491,6 +503,13 @@ static void digest_cache_inode_free_security(struct inode *inode) static struct security_hook_list digest_cache_hooks[] __ro_after_init = { LSM_HOOK_INIT(inode_alloc_security, digest_cache_inode_alloc_security), LSM_HOOK_INIT(inode_free_security, digest_cache_inode_free_security), + LSM_HOOK_INIT(path_truncate, digest_cache_path_truncate), + LSM_HOOK_INIT(file_release, digest_cache_file_release), + LSM_HOOK_INIT(inode_unlink, digest_cache_inode_unlink), + LSM_HOOK_INIT(inode_rename, digest_cache_inode_rename), + LSM_HOOK_INIT(inode_post_setxattr, digest_cache_inode_post_setxattr), + LSM_HOOK_INIT(inode_post_removexattr, + digest_cache_inode_post_removexattr), }; /** diff --git a/security/digest_cache/reset.c b/security/digest_cache/reset.c new file mode 100644 index 000000000000..e07222b0e0e8 --- /dev/null +++ b/security/digest_cache/reset.c @@ -0,0 +1,197 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2023-2024 Huawei Technologies Duesseldorf GmbH + * + * Author: Roberto Sassu <roberto.sassu@huawei.com> + * + * Reset digest cache on digest lists/directory modifications. + */ + +#define pr_fmt(fmt) "DIGEST CACHE: "fmt +#include "internal.h" + +/** + * digest_cache_reset_owner - Reset dig_owner + * @inode: Inode of the digest list/directory containing the digest list + * @reason: Reason for reset + * + * This function sets the RESET bit of the digest cache pointed to by dig_owner + * (if unset), so that digest_cache_get() and digest_cache_create() respectively + * release and clear dig_user and dig_owner in the inode security blob. This + * causes new callers of digest_cache_get() to get a new digest cache. + */ +static void digest_cache_reset_owner(struct inode *inode, const char *reason) +{ + struct digest_cache_security *dig_sec; + + dig_sec = digest_cache_get_security(inode); + if (unlikely(!dig_sec)) + return; + + mutex_lock(&dig_sec->dig_owner_mutex); + if (dig_sec->dig_owner && + !test_and_set_bit(RESET, &dig_sec->dig_owner->flags)) + pr_debug("Resetting %s (dig_owner), reason: %s\n", + dig_sec->dig_owner->path_str, reason); + mutex_unlock(&dig_sec->dig_owner_mutex); +} + +/** + * digest_cache_reset_user - Reset dig_user + * @inode: Inode of the file using the digest cache + * @reason: Reason for reset + * + * This function sets the RESET_USER bit (if unset), so that digest_cache_get() + * clears the dig_user pointer in the inode security blob and determines again + * the digest list inode to get a digest cache from. + */ +static void digest_cache_reset_user(struct inode *inode, const char *reason) +{ + struct digest_cache_security *dig_sec; + + dig_sec = digest_cache_get_security(inode); + if (unlikely(!dig_sec)) + return; + + mutex_lock(&dig_sec->dig_user_mutex); + if (dig_sec->dig_user && + !test_and_set_bit(RESET_USER, &dig_sec->dig_user->flags)) + pr_debug("Resetting %s (dig_user), reason: %s\n", + dig_sec->dig_user->path_str, reason); + mutex_unlock(&dig_sec->dig_user_mutex); +} + +/** + * digest_cache_path_truncate - A file is being truncated + * @path: File path + * + * This function is called when a file is being truncated. If the inode is a + * digest list, it resets the inode dig_owner, to force rebuilding the digest + * cache. + * + * Return: Zero. + */ +int digest_cache_path_truncate(const struct path *path) +{ + struct inode *inode = d_backing_inode(path->dentry); + + if (!S_ISREG(inode->i_mode)) + return 0; + + digest_cache_reset_owner(inode, "file_truncate"); + return 0; +} + +/** + * digest_cache_file_release - Last reference of a file desc is being released + * @file: File descriptor + * + * This function is called when the last reference of a file descriptor is + * being released. If the inode is a regular file and was opened for write, or + * the parent inode is the digest list directory and the file was created, it + * resets the inode dig_owner, to force rebuilding the digest cache. + */ +void digest_cache_file_release(struct file *file) +{ + struct inode *dir = d_backing_inode(file_dentry(file)->d_parent); + + if (!S_ISREG(file_inode(file)->i_mode) || !(file->f_mode & FMODE_WRITE)) + return; + + digest_cache_reset_owner(file_inode(file), "file_file_release"); + if (file->f_mode & FMODE_CREATED) + digest_cache_reset_owner(dir, "dir_file_release"); +} + +/** + * digest_cache_inode_unlink - An inode is being removed + * @dir: Inode of the affected directory + * @dentry: Dentry of the inode being removed + * + * This function is called when an existing inode is being removed. If the + * inode is a digest list, or the parent inode is the digest list directory and + * the inode is a regular file, it resets the affected inode dig_owner, to force + * rebuilding the digest cache. + * + * Return: Zero. + */ +int digest_cache_inode_unlink(struct inode *dir, struct dentry *dentry) +{ + struct inode *inode = d_backing_inode(dentry); + + if (!S_ISREG(inode->i_mode)) + return 0; + + digest_cache_reset_owner(inode, "file_unlink"); + digest_cache_reset_owner(dir, "dir_unlink"); + return 0; +} + +/** + * digest_cache_inode_rename - An inode is being renamed + * @old_dir: Inode of the directory containing the inode being renamed + * @old_dentry: Dentry of the inode being renamed + * @new_dir: Directory where the inode will be placed into + * @new_dentry: Dentry of the inode after being renamed + * + * This function is called when an existing inode is being moved from a + * directory to another (rename). If the inode is a digest list, or that inode + * is moved from/to the digest list directory, it resets the affected inode + * dig_owner, to force rebuilding the digest cache. + * + * Return: Zero. + */ +int digest_cache_inode_rename(struct inode *old_dir, struct dentry *old_dentry, + struct inode *new_dir, struct dentry *new_dentry) +{ + struct inode *old_inode = d_backing_inode(old_dentry); + + if (!S_ISREG(old_inode->i_mode)) + return 0; + + digest_cache_reset_owner(old_inode, "file_rename"); + digest_cache_reset_owner(old_dir, "dir_rename_from"); + digest_cache_reset_owner(new_dir, "dir_rename_to"); + return 0; +} + +/** + * digest_cache_inode_post_setxattr() - An xattr was set + * @dentry: file + * @name: xattr name + * @value: xattr value + * @size: size of xattr value + * @flags: flags + * + * This function is called after an xattr was set on an existing inode. If the + * inode points to a digest cache and the xattr set is security.digest_list, it + * resets dig_user in the inode security blob, to force retrieving a fresh + * digest cache. + */ +void digest_cache_inode_post_setxattr(struct dentry *dentry, const char *name, + const void *value, size_t size, int flags) +{ + if (strcmp(name, XATTR_NAME_DIGEST_LIST)) + return; + + digest_cache_reset_user(d_backing_inode(dentry), "file_setxattr"); +} + +/** + * digest_cache_inode_post_removexattr() - An xattr was removed + * @dentry: file + * @name: xattr name + * + * This function is called after an xattr was removed from an existing inode. + * If the inode points to a digest cache and the xattr removed is + * security.digest_list, it resets dig_user in the inode security blob, to + * force retrieving a fresh digest cache. + */ +void digest_cache_inode_post_removexattr(struct dentry *dentry, + const char *name) +{ + if (strcmp(name, XATTR_NAME_DIGEST_LIST)) + return; + + digest_cache_reset_user(d_backing_inode(dentry), "file_removexattr"); +}