[PATCH 1/2] fs/sysctl: fix potential page fault while unregistering sysctl table

[Danilo Krummrich]

proc_sys_link_fill_cache() does not take currently unregistering
sysctl tables into account, which might result into a page fault in
sysctl_follow_link() - add a check to fix it.

Signed-off-by: Danilo Krummrich <danilokrummrich@xxxxxxxxxxxxx>
---
 fs/proc/proc_sysctl.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index c5cbbdff3c3d..a0b6c647835e 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -709,6 +709,9 @@ static bool proc_sys_link_fill_cache(struct file *file,
 	bool ret = true;
 	head = sysctl_head_grab(head);
 
+	if (IS_ERR(head))
+		return false;
+
 	if (S_ISLNK(table->mode)) {
 		/* It is not an error if we can not follow the link ignore it */
 		int err = sysctl_follow_link(&head, &table);
-- 
2.14.1