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fanotify: refine the validation checks on non-dir inode mask

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Commit ceaf69f8ea ("fanotify: do not allow setting dirent events in
mask of non-dir") added restrictions about setting dirent events in the
mask of a non-dir inode mark, which does not make any sense.

For backward compatibility, these restictions were added only to new
(v5.17+) APIs.

It also does not make any sense to set the flags FAN_EVENT_ON_CHILD or
FAN_ONDIR in the mask of a non-dir inode.  Add these flags to the
dir-only restriction of the new APIs as well.

Move the check of the dir-only flags for new APIs into the helper
fanotify_events_supported(), which is only called for FAN_MARK_ADD,
because there is no need to error on an attempt to remove the dir-only
flags from non-dir inode.

Fixes: ceaf69f8ea ("fanotify: do not allow setting dirent events in mask of non-dir")
Link: https://lore.kernel.org/linux-fsdevel/20220627113224.kr2725conevh53u4@quack3.lan/
Link: https://lore.kernel.org/r/20220627174719.2838175-1-amir73il@gmail.com
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
This commit is contained in:
Amir Goldstein 2022-06-27 20:47:19 +03:00 committed by Jan Kara
parent ca1fdab7fd
commit 8698e3bab4
2 changed files with 23 additions and 15 deletions
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34
fs/notify/fanotify/fanotify_user.c
View File

@ -1513,8 +1513,15 @@ static int fanotify_test_fid(struct dentry *dentry)
return 0;
}
static int fanotify_events_supported(struct path *path, __u64 mask)
static int fanotify_events_supported(struct fsnotify_group *group,
struct path *path, __u64 mask,
unsigned int flags)
{
unsigned int mark_type = flags & FANOTIFY_MARK_TYPE_BITS;
/* Strict validation of events in non-dir inode mask with v5.17+ APIs */
bool strict_dir_events = FAN_GROUP_FLAG(group, FAN_REPORT_TARGET_FID) ||
(mask & FAN_RENAME);
/*
* Some filesystems such as 'proc' acquire unusual locks when opening
* files. For them fanotify permission events have high chances of
@ -1526,6 +1533,16 @@ static int fanotify_events_supported(struct path *path, __u64 mask)
if (mask & FANOTIFY_PERM_EVENTS &&
path->mnt->mnt_sb->s_type->fs_flags & FS_DISALLOW_NOTIFY_PERM)
return -EINVAL;
/*
* We shouldn't have allowed setting dirent events and the directory
* flags FAN_ONDIR and FAN_EVENT_ON_CHILD in mask of non-dir inode,
* but because we always allowed it, error only when using new APIs.
*/
if (strict_dir_events && mark_type == FAN_MARK_INODE &&
!d_is_dir(path->dentry) && (mask & FANOTIFY_DIRONLY_EVENT_BITS))
return -ENOTDIR;
return 0;
}
@ -1672,7 +1689,7 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
goto fput_and_out;
if (flags & FAN_MARK_ADD) {
ret = fanotify_events_supported(&path, mask);
ret = fanotify_events_supported(group, &path, mask, flags);
if (ret)
goto path_put_and_out;
}
@ -1695,19 +1712,6 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
else
mnt = path.mnt;
/*
* FAN_RENAME is not allowed on non-dir (for now).
* We shouldn't have allowed setting any dirent events in mask of
* non-dir, but because we always allowed it, error only if group
* was initialized with the new flag FAN_REPORT_TARGET_FID.
*/
ret = -ENOTDIR;
if (inode && !S_ISDIR(inode->i_mode) &&
((mask & FAN_RENAME) ||
((mask & FANOTIFY_DIRENT_EVENTS) &&
FAN_GROUP_FLAG(group, FAN_REPORT_TARGET_FID))))
goto path_put_and_out;
/* Mask out FAN_EVENT_ON_CHILD flag for sb/mount/non-dir marks */
if (mnt || !S_ISDIR(inode->i_mode)) {
mask &= ~FAN_EVENT_ON_CHILD;

4
include/linux/fanotify.h
View File

@ -111,6 +111,10 @@
FANOTIFY_PERM_EVENTS | \
FAN_Q_OVERFLOW | FAN_ONDIR)
/* Events and flags relevant only for directories */
#define FANOTIFY_DIRONLY_EVENT_BITS (FANOTIFY_DIRENT_EVENTS | \
FAN_EVENT_ON_CHILD | FAN_ONDIR)
#define ALL_FANOTIFY_EVENT_BITS (FANOTIFY_OUTGOING_EVENTS | \
FANOTIFY_EVENT_FLAGS)