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author | Amir Goldstein <amir73il@gmail.com> | 2023-10-18 12:59:56 +0300 |
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committer | Jan Kara <jack@suse.cz> | 2023-10-19 17:19:20 +0300 |
commit | 97ac489775f26acfd46a8a60c2f84ce7cc79fa4b (patch) | |
tree | 587b3b1add0bed3fad561bd242710ff53b855b0c /fs | |
parent | dd72f9c7e512da377074d47d990564959b772643 (diff) | |
download | linux-97ac489775f26acfd46a8a60c2f84ce7cc79fa4b.tar.xz |
fanotify: limit reporting of event with non-decodeable file handles
Commit a95aef69a740 ("fanotify: support reporting non-decodeable file
handles") merged in v6.5-rc1, added the ability to use an fanotify group
with FAN_REPORT_FID mode to watch filesystems that do not support nfs
export, but do know how to encode non-decodeable file handles, with the
newly introduced AT_HANDLE_FID flag.
At the time that this commit was merged, there were no filesystems
in-tree with those traits.
Commit 16aac5ad1fa9 ("ovl: support encoding non-decodable file handles"),
merged in v6.6-rc1, added this trait to overlayfs, thus allowing fanotify
watching of overlayfs with FAN_REPORT_FID mode.
In retrospect, allowing an fanotify filesystem/mount mark on such
filesystem in FAN_REPORT_FID mode will result in getting events with
file handles, without the ability to resolve the filesystem objects from
those file handles (i.e. no open_by_handle_at() support).
For v6.6, the safer option would be to allow this mode for inode marks
only, where the caller has the opportunity to use name_to_handle_at() at
the time of setting the mark. In the future we can revise this decision.
Fixes: a95aef69a740 ("fanotify: support reporting non-decodeable file handles")
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Message-Id: <20231018100000.2453965-2-amir73il@gmail.com>
Diffstat (limited to 'fs')
-rw-r--r-- | fs/notify/fanotify/fanotify_user.c | 25 |
1 files changed, 17 insertions, 8 deletions
diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c index f69c451018e3..62fe0b679e58 100644 --- a/fs/notify/fanotify/fanotify_user.c +++ b/fs/notify/fanotify/fanotify_user.c @@ -1585,16 +1585,25 @@ static int fanotify_test_fsid(struct dentry *dentry, __kernel_fsid_t *fsid) } /* Check if filesystem can encode a unique fid */ -static int fanotify_test_fid(struct dentry *dentry) +static int fanotify_test_fid(struct dentry *dentry, unsigned int flags) { + unsigned int mark_type = flags & FANOTIFY_MARK_TYPE_BITS; + const struct export_operations *nop = dentry->d_sb->s_export_op; + + /* + * We need to make sure that the filesystem supports encoding of + * file handles so user can use name_to_handle_at() to compare fids + * reported with events to the file handle of watched objects. + */ + if (!nop) + return -EOPNOTSUPP; + /* - * We need to make sure that the file system supports at least - * encoding a file handle so user can use name_to_handle_at() to - * compare fid returned with event to the file handle of watched - * objects. However, even the relaxed AT_HANDLE_FID flag requires - * at least empty export_operations for ecoding unique file ids. + * For sb/mount mark, we also need to make sure that the filesystem + * supports decoding file handles, so user has a way to map back the + * reported fids to filesystem objects. */ - if (!dentry->d_sb->s_export_op) + if (mark_type != FAN_MARK_INODE && !nop->fh_to_dentry) return -EOPNOTSUPP; return 0; @@ -1812,7 +1821,7 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask, if (ret) goto path_put_and_out; - ret = fanotify_test_fid(path.dentry); + ret = fanotify_test_fid(path.dentry, flags); if (ret) goto path_put_and_out; |