4.14-stable review patch. If anyone has any objections, please let me know.
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From: Danilo Krummrich danilokrummrich@dk-develop.de
[ Upstream commit a0b0d1c345d0317efe594df268feb5ccc99f651e ]
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 danilokrummrich@dk-develop.de Acked-by: Kees Cook keescook@chromium.org Reviewed-by: Andrew Morton akpm@linux-foundation.org Cc: "Luis R . Rodriguez" mcgrof@kernel.org Cc: "Eric W. Biederman" ebiederm@xmission.com Cc: Alexey Dobriyan adobriyan@gmail.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/proc/proc_sysctl.c | 3 +++ 1 file changed, 3 insertions(+)
--- a/fs/proc/proc_sysctl.c +++ b/fs/proc/proc_sysctl.c @@ -707,7 +707,10 @@ static bool proc_sys_link_fill_cache(str 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 */