| Message ID | Y4Dl2yjVRkJvBflq@archlinux (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Paul Moore |
| Headers | show |
| Series | [v5] evm: Correct inode_init_security hooks behaviors | expand |
On Fri, 2022-11-25 at 16:57 +0100, Nicolas Bouchinet wrote: > From: Nicolas Bouchinet <nicolas.bouchinet@ssi.gouv.fr> > > Fixes a NULL pointer dereference occurring in the > `evm_protected_xattr_common` function of the EVM LSM. The bug is > triggered if a `inode_init_security` hook returns 0 without initializing > the given `struct xattr` fields (which is the case of BPF) and if no > other LSM overrides thoses fields after. This also leads to memory > leaks. > > The `call_int_hook_xattr` macro has been inlined into the > `security_inode_init_security` hook in order to check hooks return > values and skip ones who doesn't init `xattrs`. > > Modify `evm_init_hmac` function to init the EVM hmac using every > entry of the given xattr array. > > The `MAX_LSM_EVM_XATTR` value is now based on the security modules > compiled in, which gives room for SMACK, SELinux, Apparmor, BPF and > IMA/EVM security attributes. > > Changes the default return value of the `inode_init_security` hook > definition to `-EOPNOTSUPP`. > > Changes the hook documentation to match the behavior of the LSMs using > it (only xattr->value is initialised with kmalloc and thus is the only > one that should be kfreed by the caller). > > Cc: roberto.sassu@huaweicloud.com > Signed-off-by: Nicolas Bouchinet <nicolas.bouchinet@ssi.gouv.fr> What is the relationship between this patch and Roberto's patch set? Roberto, if there is an overlap, then at minimum there should be a Reported-by tag indicating that your patch set addresses a bug reported by Nicolas.
On Tue, 2022-11-29 at 06:28 -0500, Mimi Zohar wrote: > On Fri, 2022-11-25 at 16:57 +0100, Nicolas Bouchinet wrote: > > From: Nicolas Bouchinet <nicolas.bouchinet@ssi.gouv.fr> > > > > Fixes a NULL pointer dereference occurring in the > > `evm_protected_xattr_common` function of the EVM LSM. The bug is > > triggered if a `inode_init_security` hook returns 0 without initializing > > the given `struct xattr` fields (which is the case of BPF) and if no > > other LSM overrides thoses fields after. This also leads to memory > > leaks. > > > > The `call_int_hook_xattr` macro has been inlined into the > > `security_inode_init_security` hook in order to check hooks return > > values and skip ones who doesn't init `xattrs`. > > > > Modify `evm_init_hmac` function to init the EVM hmac using every > > entry of the given xattr array. > > > > The `MAX_LSM_EVM_XATTR` value is now based on the security modules > > compiled in, which gives room for SMACK, SELinux, Apparmor, BPF and > > IMA/EVM security attributes. > > > > Changes the default return value of the `inode_init_security` hook > > definition to `-EOPNOTSUPP`. > > > > Changes the hook documentation to match the behavior of the LSMs using > > it (only xattr->value is initialised with kmalloc and thus is the only > > one that should be kfreed by the caller). > > > > Cc: roberto.sassu@huaweicloud.com > > Signed-off-by: Nicolas Bouchinet <nicolas.bouchinet@ssi.gouv.fr> > > What is the relationship between this patch and Roberto's patch set? > Roberto, if there is an overlap, then at minimum there should be a > Reported-by tag indicating that your patch set addresses a bug reported > by Nicolas. Agreed, I will add a Reported-by for the bug reported by Nicolas. For the rest, my patch set introduces a similar functionality, with the difference that it uses the reservation mechanism instead of static allocation for xattrs, as suggested by Paul. Roberto
Hi Mimi, On Tue, Nov 29, 2022 at 06:28:09AM -0500, Mimi Zohar wrote: > On Fri, 2022-11-25 at 16:57 +0100, Nicolas Bouchinet wrote: > > From: Nicolas Bouchinet <nicolas.bouchinet@ssi.gouv.fr> > > > > Fixes a NULL pointer dereference occurring in the > > `evm_protected_xattr_common` function of the EVM LSM. The bug is > > triggered if a `inode_init_security` hook returns 0 without initializing > > the given `struct xattr` fields (which is the case of BPF) and if no > > other LSM overrides thoses fields after. This also leads to memory > > leaks. > > > > The `call_int_hook_xattr` macro has been inlined into the > > `security_inode_init_security` hook in order to check hooks return > > values and skip ones who doesn't init `xattrs`. > > > > Modify `evm_init_hmac` function to init the EVM hmac using every > > entry of the given xattr array. > > > > The `MAX_LSM_EVM_XATTR` value is now based on the security modules > > compiled in, which gives room for SMACK, SELinux, Apparmor, BPF and > > IMA/EVM security attributes. > > > > Changes the default return value of the `inode_init_security` hook > > definition to `-EOPNOTSUPP`. > > > > Changes the hook documentation to match the behavior of the LSMs using > > it (only xattr->value is initialised with kmalloc and thus is the only > > one that should be kfreed by the caller). > > > > Cc: roberto.sassu@huaweicloud.com > > Signed-off-by: Nicolas Bouchinet <nicolas.bouchinet@ssi.gouv.fr> > > What is the relationship between this patch and Roberto's patch set? > Roberto, if there is an overlap, then at minimum there should be a > Reported-by tag indicating that your patch set addresses a bug reported > by Nicolas. This patch fixes the EVM NULL pointer dereference I have reported, and additionally improves the stackability of this LSM hook. This latter improvement was originally addressed by Roberto's patchset, and thus I see no problem for my fix to be merged within his patchset. > > -- > thanks, > > Mimi > Thanks for your time, Nicolas Bouchinet
On Tue, 2022-11-29 at 13:58 +0100, Nicolas Bouchinet wrote: > Hi Mimi, > > On Tue, Nov 29, 2022 at 06:28:09AM -0500, Mimi Zohar wrote: > > On Fri, 2022-11-25 at 16:57 +0100, Nicolas Bouchinet wrote: > > > From: Nicolas Bouchinet <nicolas.bouchinet@ssi.gouv.fr> > > > > > > Fixes a NULL pointer dereference occurring in the > > > `evm_protected_xattr_common` function of the EVM LSM. The bug is > > > triggered if a `inode_init_security` hook returns 0 without initializing > > > the given `struct xattr` fields (which is the case of BPF) and if no > > > other LSM overrides thoses fields after. This also leads to memory > > > leaks. > > > > > > The `call_int_hook_xattr` macro has been inlined into the > > > `security_inode_init_security` hook in order to check hooks return > > > values and skip ones who doesn't init `xattrs`. > > > > > > Modify `evm_init_hmac` function to init the EVM hmac using every > > > entry of the given xattr array. > > > > > > The `MAX_LSM_EVM_XATTR` value is now based on the security modules > > > compiled in, which gives room for SMACK, SELinux, Apparmor, BPF and > > > IMA/EVM security attributes. > > > > > > Changes the default return value of the `inode_init_security` hook > > > definition to `-EOPNOTSUPP`. > > > > > > Changes the hook documentation to match the behavior of the LSMs using > > > it (only xattr->value is initialised with kmalloc and thus is the only > > > one that should be kfreed by the caller). > > > > > > Cc: roberto.sassu@huaweicloud.com > > > Signed-off-by: Nicolas Bouchinet <nicolas.bouchinet@ssi.gouv.fr> > > > > What is the relationship between this patch and Roberto's patch set? > > Roberto, if there is an overlap, then at minimum there should be a > > Reported-by tag indicating that your patch set addresses a bug reported > > by Nicolas. > > This patch fixes the EVM NULL pointer dereference I have reported, and additionally > improves the stackability of this LSM hook. This latter improvement was originally > addressed by Roberto's patchset, and thus I see no problem for my fix to be merged > within his patchset. + if (!num_filled_xattrs) goto out; - evm_xattr = lsm_xattr + 1; - ret = evm_inode_init_security(inode, lsm_xattr, evm_xattr); + ret = evm_inode_init_security(inode, new_xattrs, + new_xattrs + num_filled_xattrs); This part of patch 4 should be enough to fix the issue, until EVM is outside the LSM infrastructure. It prevents EVM from being called if there are no xattrs filled (the panic occurred due to xattr->name being NULL). Then, this part of patch 6: + for (xattr = xattrs; xattr->value != NULL; xattr++) { + if (evm_protected_xattr(xattr->name)) + evm_protected_xattrs = true; + } + + /* EVM xattr not needed. */ + if (!evm_protected_xattrs) + return -EOPNOTSUPP; should be sufficient for when EVM is managed by the LSM infrastructure. security_check_compact_filled_xattrs() ensures that if xattr->value is not NULL, xattr->name is not NULL too. Roberto > > -- > > thanks, > > > > Mimi > > > > Thanks for your time, > > Nicolas Bouchinet
Hi Roberto, On Tue, Nov 29, 2022 at 02:10:06PM +0100, Roberto Sassu wrote: > On Tue, 2022-11-29 at 13:58 +0100, Nicolas Bouchinet wrote: > > Hi Mimi, > > > > On Tue, Nov 29, 2022 at 06:28:09AM -0500, Mimi Zohar wrote: > > > On Fri, 2022-11-25 at 16:57 +0100, Nicolas Bouchinet wrote: > > > > From: Nicolas Bouchinet <nicolas.bouchinet@ssi.gouv.fr> > > > > > > > > Fixes a NULL pointer dereference occurring in the > > > > `evm_protected_xattr_common` function of the EVM LSM. The bug is > > > > triggered if a `inode_init_security` hook returns 0 without initializing > > > > the given `struct xattr` fields (which is the case of BPF) and if no > > > > other LSM overrides thoses fields after. This also leads to memory > > > > leaks. > > > > > > > > The `call_int_hook_xattr` macro has been inlined into the > > > > `security_inode_init_security` hook in order to check hooks return > > > > values and skip ones who doesn't init `xattrs`. > > > > > > > > Modify `evm_init_hmac` function to init the EVM hmac using every > > > > entry of the given xattr array. > > > > > > > > The `MAX_LSM_EVM_XATTR` value is now based on the security modules > > > > compiled in, which gives room for SMACK, SELinux, Apparmor, BPF and > > > > IMA/EVM security attributes. > > > > > > > > Changes the default return value of the `inode_init_security` hook > > > > definition to `-EOPNOTSUPP`. > > > > > > > > Changes the hook documentation to match the behavior of the LSMs using > > > > it (only xattr->value is initialised with kmalloc and thus is the only > > > > one that should be kfreed by the caller). > > > > > > > > Cc: roberto.sassu@huaweicloud.com > > > > Signed-off-by: Nicolas Bouchinet <nicolas.bouchinet@ssi.gouv.fr> > > > > > > What is the relationship between this patch and Roberto's patch set? > > > Roberto, if there is an overlap, then at minimum there should be a > > > Reported-by tag indicating that your patch set addresses a bug reported > > > by Nicolas. > > > > This patch fixes the EVM NULL pointer dereference I have reported, and additionally > > improves the stackability of this LSM hook. This latter improvement was originally > > addressed by Roberto's patchset, and thus I see no problem for my fix to be merged > > within his patchset. > > + if (!num_filled_xattrs) > goto out; > > - evm_xattr = lsm_xattr + 1; > - ret = evm_inode_init_security(inode, lsm_xattr, evm_xattr); > + ret = evm_inode_init_security(inode, new_xattrs, > + new_xattrs + num_filled_xattrs); > > This part of patch 4 should be enough to fix the issue, until EVM is > outside the LSM infrastructure. > > It prevents EVM from being called if there are no xattrs filled (the > panic occurred due to xattr->name being NULL). > > Then, this part of patch 6: > > + for (xattr = xattrs; xattr->value != NULL; xattr++) { > + if (evm_protected_xattr(xattr->name)) > + evm_protected_xattrs = true; > + } > + > + /* EVM xattr not needed. */ > + if (!evm_protected_xattrs) > + return -EOPNOTSUPP; > > should be sufficient for when EVM is managed by the LSM infrastructure. > > security_check_compact_filled_xattrs() ensures that if xattr->value is > not NULL, xattr->name is not NULL too. > I think a Reported-by tag should enougth then ! > Roberto > > > > -- > > > thanks, > > > > > > Mimi > > > > > > > Thanks for your time, > > > > Nicolas Bouchinet > Thanks ! Nicolas Bouchinet
On Tue, 2022-11-29 at 15:31 +0100, Nicolas Bouchinet wrote: > Hi Roberto, > > On Tue, Nov 29, 2022 at 02:10:06PM +0100, Roberto Sassu wrote: > > On Tue, 2022-11-29 at 13:58 +0100, Nicolas Bouchinet wrote: > > > Hi Mimi, > > > > > > On Tue, Nov 29, 2022 at 06:28:09AM -0500, Mimi Zohar wrote: > > > > On Fri, 2022-11-25 at 16:57 +0100, Nicolas Bouchinet wrote: > > > > > From: Nicolas Bouchinet <nicolas.bouchinet@ssi.gouv.fr> > > > > > > > > > > Fixes a NULL pointer dereference occurring in the > > > > > `evm_protected_xattr_common` function of the EVM LSM. The bug is > > > > > triggered if a `inode_init_security` hook returns 0 without initializing > > > > > the given `struct xattr` fields (which is the case of BPF) and if no > > > > > other LSM overrides thoses fields after. This also leads to memory > > > > > leaks. > > > > > > > > > > The `call_int_hook_xattr` macro has been inlined into the > > > > > `security_inode_init_security` hook in order to check hooks return > > > > > values and skip ones who doesn't init `xattrs`. > > > > > > > > > > Modify `evm_init_hmac` function to init the EVM hmac using every > > > > > entry of the given xattr array. > > > > > > > > > > The `MAX_LSM_EVM_XATTR` value is now based on the security modules > > > > > compiled in, which gives room for SMACK, SELinux, Apparmor, BPF and > > > > > IMA/EVM security attributes. > > > > > > > > > > Changes the default return value of the `inode_init_security` hook > > > > > definition to `-EOPNOTSUPP`. > > > > > > > > > > Changes the hook documentation to match the behavior of the LSMs using > > > > > it (only xattr->value is initialised with kmalloc and thus is the only > > > > > one that should be kfreed by the caller). > > > > > > > > > > Cc: roberto.sassu@huaweicloud.com > > > > > Signed-off-by: Nicolas Bouchinet <nicolas.bouchinet@ssi.gouv.fr> > > > > > > > > What is the relationship between this patch and Roberto's patch set? > > > > Roberto, if there is an overlap, then at minimum there should be a > > > > Reported-by tag indicating that your patch set addresses a bug reported > > > > by Nicolas. > > > > > > This patch fixes the EVM NULL pointer dereference I have reported, and additionally > > > improves the stackability of this LSM hook. This latter improvement was originally > > > addressed by Roberto's patchset, and thus I see no problem for my fix to be merged > > > within his patchset. > > > > + if (!num_filled_xattrs) > > goto out; > > > > - evm_xattr = lsm_xattr + 1; > > - ret = evm_inode_init_security(inode, lsm_xattr, evm_xattr); > > + ret = evm_inode_init_security(inode, new_xattrs, > > + new_xattrs + num_filled_xattrs); > > > > This part of patch 4 should be enough to fix the issue, until EVM is > > outside the LSM infrastructure. > > > > It prevents EVM from being called if there are no xattrs filled (the > > panic occurred due to xattr->name being NULL). > > > > Then, this part of patch 6: > > > > + for (xattr = xattrs; xattr->value != NULL; xattr++) { > > + if (evm_protected_xattr(xattr->name)) > > + evm_protected_xattrs = true; > > + } > > + > > + /* EVM xattr not needed. */ > > + if (!evm_protected_xattrs) > > + return -EOPNOTSUPP; > > > > should be sufficient for when EVM is managed by the LSM infrastructure. > > > > security_check_compact_filled_xattrs() ensures that if xattr->value is > > not NULL, xattr->name is not NULL too. > > > I think a Reported-by tag should enougth then ! Perfect, will do. Thanks for reporting the issue. Roberto > > Roberto > > > > > > -- > > > > thanks, > > > > > > > > Mimi > > > > > > > > > > Thanks for your time, > > > > > > Nicolas Bouchinet > > Thanks ! > Nicolas Bouchinet
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h index ec119da1d89b4..0ba396f08c4f1 100644 --- a/include/linux/lsm_hook_defs.h +++ b/include/linux/lsm_hook_defs.h @@ -111,7 +111,7 @@ LSM_HOOK(int, 0, path_notify, const struct path *path, u64 mask, unsigned int obj_type) LSM_HOOK(int, 0, inode_alloc_security, struct inode *inode) LSM_HOOK(void, LSM_RET_VOID, inode_free_security, struct inode *inode) -LSM_HOOK(int, 0, inode_init_security, struct inode *inode, +LSM_HOOK(int, -EOPNOTSUPP, inode_init_security, struct inode *inode, struct inode *dir, const struct qstr *qstr, const char **name, void **value, size_t *len) LSM_HOOK(int, 0, inode_init_security_anon, struct inode *inode, diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index 4ec80b96c22e7..8a2762f7e75f5 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -229,15 +229,15 @@ * This hook is called by the fs code as part of the inode creation * transaction and provides for atomic labeling of the inode, unlike * the post_create/mkdir/... hooks called by the VFS. The hook function - * is expected to allocate the name and value via kmalloc, with the caller - * being responsible for calling kfree after using them. + * is expected to allocate the value via kmalloc, with the caller + * being responsible for calling kfree after using it. * If the security module does not use security attributes or does * not wish to put a security attribute on this particular inode, * then it should return -EOPNOTSUPP to skip this processing. * @inode contains the inode structure of the newly created inode. * @dir contains the inode structure of the parent directory. * @qstr contains the last path component of the new object - * @name will be set to the allocated name suffix (e.g. selinux). + * @name will be set to a name suffix (e.g. selinux). * @value will be set to the allocated attribute value. * @len will be set to the length of the value. * Returns 0 if @name and @value have been successfully set, diff --git a/security/integrity/evm/evm.h b/security/integrity/evm/evm.h index f8b8c5004fc7c..6d9628ca7c246 100644 --- a/security/integrity/evm/evm.h +++ b/security/integrity/evm/evm.h @@ -61,5 +61,6 @@ int evm_calc_hash(struct dentry *dentry, const char *req_xattr_name, int evm_init_hmac(struct inode *inode, const struct xattr *xattr, char *hmac_val); int evm_init_secfs(void); +int evm_protected_xattr(const char *req_xattr_name); #endif diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c index 708de9656bbd2..06639f3cfb383 100644 --- a/security/integrity/evm/evm_crypto.c +++ b/security/integrity/evm/evm_crypto.c @@ -385,7 +385,7 @@ int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name, return rc; } -int evm_init_hmac(struct inode *inode, const struct xattr *lsm_xattr, +int evm_init_hmac(struct inode *inode, const struct xattr *lsm_xattrs, char *hmac_val) { struct shash_desc *desc; @@ -396,7 +396,12 @@ int evm_init_hmac(struct inode *inode, const struct xattr *lsm_xattr, return PTR_ERR(desc); } - crypto_shash_update(desc, lsm_xattr->value, lsm_xattr->value_len); + for (int i = 0; lsm_xattrs[i].value != NULL; i++) { + if (evm_protected_xattr(lsm_xattrs[i].name)) + crypto_shash_update(desc, + lsm_xattrs[i].value, + lsm_xattrs[i].value_len); + } hmac_add_misc(desc, inode, EVM_XATTR_HMAC, hmac_val); kfree(desc); return 0; diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c index 23d484e05e6f2..35a060a6124c5 100644 --- a/security/integrity/evm/evm_main.c +++ b/security/integrity/evm/evm_main.c @@ -305,7 +305,7 @@ static int evm_protected_xattr_common(const char *req_xattr_name, return found; } -static int evm_protected_xattr(const char *req_xattr_name) +int evm_protected_xattr(const char *req_xattr_name) { return evm_protected_xattr_common(req_xattr_name, false); } @@ -852,8 +852,7 @@ int evm_inode_init_security(struct inode *inode, struct evm_xattr *xattr_data; int rc; - if (!(evm_initialized & EVM_INIT_HMAC) || - !evm_protected_xattr(lsm_xattr->name)) + if (!(evm_initialized & EVM_INIT_HMAC)) return 0; xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS); diff --git a/security/security.c b/security/security.c index 79d82cb6e4696..6cdd3fdc08fbc 100644 --- a/security/security.c +++ b/security/security.c @@ -30,7 +30,11 @@ #include <linux/msg.h> #include <net/flow.h> -#define MAX_LSM_EVM_XATTR 2 +#define MAX_LSM_EVM_XATTR \ + ((IS_ENABLED(CONFIG_EVM) ? 1 : 0) + \ + (IS_ENABLED(CONFIG_SECURITY_SELINUX) ? 1 : 0) + \ + (IS_ENABLED(CONFIG_SECURITY_SMACK) ? 1 : 0) + \ + (IS_ENABLED(CONFIG_BPF_LSM) ? 1 : 0)) /* How many LSMs were built into the kernel? */ #define LSM_COUNT (__end_lsm_info - __start_lsm_info) @@ -1093,9 +1097,11 @@ int security_inode_init_security(struct inode *inode, struct inode *dir, const struct qstr *qstr, const initxattrs initxattrs, void *fs_data) { + int initialized_lsms = 0; + int ret = -EOPNOTSUPP; struct xattr new_xattrs[MAX_LSM_EVM_XATTR + 1]; struct xattr *lsm_xattr, *evm_xattr, *xattr; - int ret; + struct security_hook_list *hook_ptr; if (unlikely(IS_PRIVATE(inode))) return 0; @@ -1105,15 +1111,30 @@ int security_inode_init_security(struct inode *inode, struct inode *dir, dir, qstr, NULL, NULL, NULL); memset(new_xattrs, 0, sizeof(new_xattrs)); lsm_xattr = new_xattrs; - ret = call_int_hook(inode_init_security, -EOPNOTSUPP, inode, dir, qstr, - &lsm_xattr->name, - &lsm_xattr->value, - &lsm_xattr->value_len); - if (ret) + hlist_for_each_entry(hook_ptr, &security_hook_heads.inode_init_security, + list) { + ret = hook_ptr->hook.inode_init_security(inode, dir, qstr, + &lsm_xattr->name, + &lsm_xattr->value, + &lsm_xattr->value_len); + if (ret == -EOPNOTSUPP) + continue; + if (ret != 0) + goto out; + if (WARN_ON_ONCE(initialized_lsms >= MAX_LSM_EVM_XATTR || + !lsm_xattr->name || + !lsm_xattr->value)) { + ret = -ENOMEM; + goto out; + } + lsm_xattr++; + initialized_lsms++; + } + if (!initialized_lsms) goto out; - evm_xattr = lsm_xattr + 1; - ret = evm_inode_init_security(inode, lsm_xattr, evm_xattr); + evm_xattr = lsm_xattr; + ret = evm_inode_init_security(inode, new_xattrs, evm_xattr); if (ret) goto out; ret = initxattrs(inode, new_xattrs, fs_data);