On 2018-02-28 00:02, Kees Cook wrote:
On Tue, Feb 27, 2018 at 2:43 PM, Danilo Krummrich
<danilokrummrich@xxxxxxxxxxxxx> wrote:
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;
Nothing appears to actually change "ret" in this function. It should
likely be dropped too.
proc_sys_fill_cache() potentially changes "ret".
head = sysctl_head_grab(head);
+ if (IS_ERR(head))
+ return false;
+
This looks sensible. I'd drop the blank line between sysctl_head_grab
and the IS_ERR, though.
I'll do that.
How are you testing this change?
Honestly, not at all. Actually, I never run in such a page fault.
I spotted it by accident while reading the code.
Thanks!
-Kees
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
