4.16-stable review patch. If anyone has any objections, please let me know.
------------------ From: Danilo Krummrich <[email protected]> [ 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/[email protected] Fixes: 0e47c99d7fe25 ("sysctl: Replace root_list with links between sysctl_table_sets") Signed-off-by: Danilo Krummrich <[email protected]> Acked-by: Kees Cook <[email protected]> Reviewed-by: Andrew Morton <[email protected]> Cc: "Luis R . Rodriguez" <[email protected]> Cc: "Eric W. Biederman" <[email protected]> Cc: Alexey Dobriyan <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Sasha Levin <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- 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 */
