| Message ID | 20170729002626.GA6759@debian.home (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, Jul 28, 2017 at 09:26:29PM -0300, Ernesto A. Fernández wrote: > When changing a file's acl mask, btrfs_set_acl() will first set the > group bits of i_mode to the value of the mask, and only then set the > actual extended attribute representing the new acl. > > If the second part fails (due to lack of space, for example) and the > file had no acl attribute to begin with, the system will from now on > assume that the mask permission bits are actual group permission bits, > potentially granting access to the wrong users. > > Prevent this by starting the journal transaction before calling > __btrfs_set_acl and only changing the inode mode after it returns > successfully. > > Signed-off-by: Ernesto A. Fernández <ernesto.mnd.fernandez@gmail.com> > --- > This issue is covered by generic/449 in xfstests. Several filesystems > are affected; some of them have already applied patches: > - fe26569 ext2: preserve i_mode if ext2_set_acl() fails > - f070e5a jfs: preserve i_mode if __jfs_set_acl() fails > - fcea8ae reiserfs: preserve i_mode if __reiserfs_set_acl() fails > > fs/btrfs/acl.c | 29 ++++++++++++++++++++++++++--- > 1 file changed, 26 insertions(+), 3 deletions(-) > > diff --git a/fs/btrfs/acl.c b/fs/btrfs/acl.c > index 8d8370d..d041526 100644 > --- a/fs/btrfs/acl.c > +++ b/fs/btrfs/acl.c > @@ -27,6 +27,7 @@ > #include "ctree.h" > #include "btrfs_inode.h" > #include "xattr.h" > +#include "transaction.h" > > struct posix_acl *btrfs_get_acl(struct inode *inode, int type) > { > @@ -113,14 +114,36 @@ static int __btrfs_set_acl(struct btrfs_trans_handle *trans, > > int btrfs_set_acl(struct inode *inode, struct posix_acl *acl, int type) > { > + struct btrfs_root *root = BTRFS_I(inode)->root; > + struct btrfs_trans_handle *trans; > int ret; > + umode_t mode = inode->i_mode; > + > + if (btrfs_root_readonly(root)) > + return -EROFS; > + > + trans = btrfs_start_transaction(root, 2); > + if (IS_ERR(trans)) > + return PTR_ERR(trans); > > if (type == ACL_TYPE_ACCESS && acl) { > - ret = posix_acl_update_mode(inode, &inode->i_mode, &acl); > + ret = posix_acl_update_mode(inode, &mode, &acl); > if (ret) > - return ret; > + goto out; > } > - return __btrfs_set_acl(NULL, inode, acl, type); > + ret = __btrfs_set_acl(trans, inode, acl, type); > + if (ret) > + goto out; > + > + inode->i_mode = mode; > + inode_inc_iversion(inode); > + inode->i_ctime = current_time(inode); > + set_bit(BTRFS_INODE_COPY_EVERYTHING, &BTRFS_I(inode)->runtime_flags); This only needs to be set if we actually set the xattr. I'd fix setxattr to call it every time it's called. > + ret = btrfs_update_inode(trans, root, inode); > + BUG_ON(ret); No BUG_ON, return the error. Thanks, Josef -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Sat, Jul 29, 2017 at 12:48:04AM +0000, Josef Bacik wrote: > On Fri, Jul 28, 2017 at 09:26:29PM -0300, Ernesto A. Fernández wrote: > > + ret = __btrfs_set_acl(trans, inode, acl, type); > > + if (ret) > > + goto out; > > + > > + inode->i_mode = mode; > > + inode_inc_iversion(inode); > > + inode->i_ctime = current_time(inode); > > + set_bit(BTRFS_INODE_COPY_EVERYTHING, &BTRFS_I(inode)->runtime_flags); > > This only needs to be set if we actually set the xattr. I'd fix setxattr to > call it every time it's called. I had not thought of that, thank you. If I'm understanding this correctly the issue would be only when setting a NULL default acl on an inode that is not a directory. In that case I probably shouldn't be calling btrfs_update_inode either, but I can't move that back to setxattr. Perhaps __btrfs_set_acl could return an error in that case, like -ENOTDIR, and then we can set ret back to 0 before returning from btrfs_set_acl. > > + ret = btrfs_update_inode(trans, root, inode); > > + BUG_ON(ret); > > No BUG_ON, return the error. The call to BUG_ON was already there before my patch, only inside the __btrfs_setxattr function. Since I didn't know the reason I thought it was best not to change it. I'll do as you say in the next version. Thank you for your review. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/btrfs/acl.c b/fs/btrfs/acl.c index 8d8370d..d041526 100644 --- a/fs/btrfs/acl.c +++ b/fs/btrfs/acl.c @@ -27,6 +27,7 @@ #include "ctree.h" #include "btrfs_inode.h" #include "xattr.h" +#include "transaction.h" struct posix_acl *btrfs_get_acl(struct inode *inode, int type) { @@ -113,14 +114,36 @@ static int __btrfs_set_acl(struct btrfs_trans_handle *trans, int btrfs_set_acl(struct inode *inode, struct posix_acl *acl, int type) { + struct btrfs_root *root = BTRFS_I(inode)->root; + struct btrfs_trans_handle *trans; int ret; + umode_t mode = inode->i_mode; + + if (btrfs_root_readonly(root)) + return -EROFS; + + trans = btrfs_start_transaction(root, 2); + if (IS_ERR(trans)) + return PTR_ERR(trans); if (type == ACL_TYPE_ACCESS && acl) { - ret = posix_acl_update_mode(inode, &inode->i_mode, &acl); + ret = posix_acl_update_mode(inode, &mode, &acl); if (ret) - return ret; + goto out; } - return __btrfs_set_acl(NULL, inode, acl, type); + ret = __btrfs_set_acl(trans, inode, acl, type); + if (ret) + goto out; + + inode->i_mode = mode; + inode_inc_iversion(inode); + inode->i_ctime = current_time(inode); + set_bit(BTRFS_INODE_COPY_EVERYTHING, &BTRFS_I(inode)->runtime_flags); + ret = btrfs_update_inode(trans, root, inode); + BUG_ON(ret); +out: + btrfs_end_transaction(trans); + return ret; } /*
When changing a file's acl mask, btrfs_set_acl() will first set the group bits of i_mode to the value of the mask, and only then set the actual extended attribute representing the new acl. If the second part fails (due to lack of space, for example) and the file had no acl attribute to begin with, the system will from now on assume that the mask permission bits are actual group permission bits, potentially granting access to the wrong users. Prevent this by starting the journal transaction before calling __btrfs_set_acl and only changing the inode mode after it returns successfully. Signed-off-by: Ernesto A. Fernández <ernesto.mnd.fernandez@gmail.com> --- This issue is covered by generic/449 in xfstests. Several filesystems are affected; some of them have already applied patches: - fe26569 ext2: preserve i_mode if ext2_set_acl() fails - f070e5a jfs: preserve i_mode if __jfs_set_acl() fails - fcea8ae reiserfs: preserve i_mode if __reiserfs_set_acl() fails fs/btrfs/acl.c | 29 ++++++++++++++++++++++++++--- 1 file changed, 26 insertions(+), 3 deletions(-)