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Commit e7099d8a authored by Eric Paris's avatar Eric Paris
Browse files

fanotify: limit the number of marks in a single fanotify group 



There is currently no limit on the number of marks a given fanotify group
can have.  Since fanotify is gated on CAP_SYS_ADMIN this was not seen as
a serious DoS threat.  This patch implements a default of 8192, the same as
inotify to work towards removing the CAP_SYS_ADMIN gating and eliminating
the default DoS'able status.

Signed-off-by: default avatarEric Paris <eparis@redhat.com>
parent 5dd03f55

fs/notify/fanotify/fanotify_user.c

+9 −0
Original line number Diff line number Diff line
@@ -17,6 +17,7 @@ 
#include <asm/ioctls.h>



#define FANOTIFY_DEFAULT_MAX_EVENTS	16384

#define FANOTIFY_DEFAULT_MAX_MARKS	8192



extern const struct fsnotify_ops fanotify_fsnotify_ops;
@@ -584,6 +585,9 @@ static int fanotify_add_vfsmount_mark(struct fsnotify_group *group, 
	if (!fsn_mark) {

		int ret;



		if (atomic_read(&group->num_marks) > group->fanotify_data.max_marks)

			return -ENOSPC;



		fsn_mark = kmem_cache_alloc(fanotify_mark_cache, GFP_KERNEL);

		if (!fsn_mark)

			return -ENOMEM;
@@ -626,6 +630,9 @@ static int fanotify_add_inode_mark(struct fsnotify_group *group, 
	if (!fsn_mark) {

		int ret;



		if (atomic_read(&group->num_marks) > group->fanotify_data.max_marks)

			return -ENOSPC;



		fsn_mark = kmem_cache_alloc(fanotify_mark_cache, GFP_KERNEL);

		if (!fsn_mark)

			return -ENOMEM;
@@ -700,6 +707,8 @@ 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;



	fd = anon_inode_getfd("[fanotify]", &fanotify_fops, group, f_flags);

	if (fd < 0)

		goto out_put_group;

include/linux/fsnotify_backend.h

+1 −0
Original line number Diff line number Diff line
@@ -169,6 +169,7 @@ struct fsnotify_group { 
			bool bypass_perm; /* protected by access_mutex */

#endif /* CONFIG_FANOTIFY_ACCESS_PERMISSIONS */

			int f_flags;

			unsigned int max_marks;

		} fanotify_data;

#endif /* CONFIG_FANOTIFY */

	};