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. Fixes: 0e47c99d7fe25 ("sysctl: Replace root_list with links between sysctl_table_sets") Cc: stable@vger.kernel.org Acked-by: Kees Cook <keescook@chromium.org> Signed-off-by: Danilo Krummrich <danilokrummrich@dk-develop.de> --- v2: removed empty line between between sysctl_head_grab and IS_ERR v3: extend commit message, add tags and cc stable --- 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..82ac5f682b73 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 */ -- 2.14.1
proc_sys_link_fill_cache() does not need to check whether we're called for a link - it's already done by scan(). Acked-by: Kees Cook <keescook@chromium.org> Signed-off-by: Danilo Krummrich <danilokrummrich@dk-develop.de> --- v2: removed 'err' as it's only used for sysctl_follow_link() v3: add ack --- fs/proc/proc_sysctl.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c index 82ac5f682b73..d36ef667c0a8 100644 --- a/fs/proc/proc_sysctl.c +++ b/fs/proc/proc_sysctl.c @@ -712,12 +712,9 @@ static bool proc_sys_link_fill_cache(struct file *file, 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); - if (err) - goto out; - } + /* It is not an error if we can not follow the link ignore it */ + if (sysctl_follow_link(&head, &table)) + goto out; ret = proc_sys_fill_cache(file, ctx, head, table); out: -- 2.14.1