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fanotify: allow userspace to override max marks

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Some fanotify groups, especially those like AV scanners, will need to place
lots of marks, particularly ignore marks.  Since ignore marks do not pin
inodes in cache and are cleared if the inode is removed from core (usually
under memory pressure) we expose an interface for listeners, with
CAP_SYS_ADMIN, to override the maximum number of marks and be allowed to
set and 'unlimited' number of marks.  Programs which make use of this
feature will be able to OOM a machine.

Signed-off-by: Eric Paris <eparis@redhat.com>
This commit is contained in:
Eric Paris 2010-10-28 17:21:58 -04:00
parent e7099d8a5a
commit ac7e22dcfa
2 changed files with 11 additions and 2 deletions
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9
fs/notify/fanotify/fanotify_user.c
View file

@ -707,7 +707,14 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
group->max_events = FANOTIFY_DEFAULT_MAX_EVENTS;
}
group->fanotify_data.max_marks = FANOTIFY_DEFAULT_MAX_MARKS;
if (flags & FAN_UNLIMITED_MARKS) {
fd = -EPERM;
if (!capable(CAP_SYS_ADMIN))
goto out_put_group;
group->fanotify_data.max_marks = UINT_MAX;
} else {
group->fanotify_data.max_marks = FANOTIFY_DEFAULT_MAX_MARKS;
}
fd = anon_inode_getfd("[fanotify]", &fanotify_fops, group, f_flags);
if (fd < 0)

4
include/linux/fanotify.h
View file

@ -32,9 +32,11 @@
FAN_CLASS_PRE_CONTENT)
#define FAN_UNLIMITED_QUEUE 0x00000010
#define FAN_UNLIMITED_MARKS 0x00000020
#define FAN_ALL_INIT_FLAGS (FAN_CLOEXEC | FAN_NONBLOCK | \
FAN_ALL_CLASS_BITS | FAN_UNLIMITED_QUEUE)
FAN_ALL_CLASS_BITS | FAN_UNLIMITED_QUEUE |\
FAN_UNLIMITED_MARKS)
/* flags used for fanotify_modify_mark() */
#define FAN_MARK_ADD 0x00000001