fsnotify: implement a default maximum queue depth

Currently fanotify has no maximum queue depth. Since fanotify is CAP_SYS_ADMIN only this does not pose a normal user DoS issue, but it certianly is possible that an fanotify listener which can't keep up could OOM the box. This patch implements a default 16k depth. This is the same default depth used by inotify, but given fanotify's better queue merging in many situations this queue will contain many additional useful events by comparison. Signed-off-by: Eric Paris <eparis@redhat.com>

fsnotify: implement a default maximum queue depth
Currently fanotify has no maximum queue depth. Since fanotify is CAP_SYS_ADMIN only this does not pose a normal user DoS issue, but it certianly is possible that an fanotify listener which can't keep up could OOM the box. This patch implements a default 16k depth. This is the same default depth used by inotify, but given fanotify's better queue merging in many situations this queue will contain many additional useful events by comparison. Signed-off-by: Eric Paris <eparis@redhat.com>
Eric Paris
1 parent 5322a59f14
Showing 2 changed files with 4 additions and 1 deletions Side-by-side Diff
fs/notify/fanotify/fanotify_user.c
include/linux/fanotify.h
@@ -16,6 +16,8 @@
  
 #include <asm/ioctls.h>
  
+#define FANOTIFY_DEFAULT_MAX_EVENTS	16384
+
 extern const struct fsnotify_ops fanotify_fsnotify_ops;
  
 static struct kmem_cache *fanotify_mark_cache __read_mostly;
@@ -688,6 +690,8 @@
 		fd = -EINVAL;
 		goto out_put_group;
 	}
+
+	group->max_events = FANOTIFY_DEFAULT_MAX_EVENTS;
  
 	fd = anon_inode_getfd("[fanotify]", &fanotify_fops, group, f_flags);
 	if (fd < 0)
@@ -12,7 +12,6 @@
  
 #define FAN_EVENT_ON_CHILD	0x08000000	/* interested in child events */
  
-/* FIXME currently Q's have no limit.... */
 #define FAN_Q_OVERFLOW		0x00004000	/* Event queued overflowed */
  
 #define FAN_OPEN_PERM		0x00010000	/* File open in perm check */
...	...	@@ -16,6 +16,8 @@
16	16
17	17	#include <asm/ioctls.h>
18	18
	19	+#define FANOTIFY_DEFAULT_MAX_EVENTS 16384
	20	+
19	21	extern const struct fsnotify_ops fanotify_fsnotify_ops;
20	22
21	23	static struct kmem_cache *fanotify_mark_cache __read_mostly;
...	...	@@ -688,6 +690,8 @@
688	690	fd = -EINVAL;
689	691	goto out_put_group;
690	692	}
	693	+
	694	+ group->max_events = FANOTIFY_DEFAULT_MAX_EVENTS;
691	695
692	696	fd = anon_inode_getfd("[fanotify]", &fanotify_fops, group, f_flags);
693	697	if (fd < 0)
...	...	@@ -12,7 +12,6 @@
12	12
13	13	#define FAN_EVENT_ON_CHILD 0x08000000 /* interested in child events */
14	14
15		-/* FIXME currently Q's have no limit.... */
16	15	#define FAN_Q_OVERFLOW 0x00004000 /* Event queued overflowed */
17	16
18	17	#define FAN_OPEN_PERM 0x00010000 /* File open in perm check */