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: Eric Paris <eparis@xxxxxxxxxx>
---
fs/notify/fanotify/fanotify_user.c | 9 +++++++++
include/linux/fsnotify_backend.h | 1 +
2 files changed, 10 insertions(+), 0 deletions(-)
diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 43d66d9..1d33d7d 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -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;
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index b37f3a7..49ceed6 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -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 */
};
--
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