From a0b0d1c345d0317efe594df268feb5ccc99f651e Mon Sep 17 00:00:00 2001 From: Danilo Krummrich Date: Tue, 10 Apr 2018 16:31:38 -0700 Subject: fs/proc/proc_sysctl.c: fix potential page fault while unregistering sysctl table 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. This bug has been present since v3.4. Link: http://lkml.kernel.org/r/20180228013506.4915-1-danilokrummrich@dk-develop.de Fixes: 0e47c99d7fe25 ("sysctl: Replace root_list with links between sysctl_table_sets") Signed-off-by: Danilo Krummrich Acked-by: Kees Cook Reviewed-by: Andrew Morton Cc: "Luis R . Rodriguez" Cc: "Eric W. Biederman" Cc: Alexey Dobriyan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- 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 c41ab261397d..7da10e595297 100644 --- a/fs/proc/proc_sysctl.c +++ b/fs/proc/proc_sysctl.c @@ -707,7 +707,10 @@ static bool proc_sys_link_fill_cache(struct file *file, struct ctl_table *table) { 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 */ -- cgit v1.2.3-59-g8ed1b