tree 598b4f990432c2c540bd19f1e619da12f6e53a85
parent 03fd4b865e5bbef57deef31599ee4bf80cf03165
author Linus Torvalds <torvalds@linux-foundation.org> 1503260787 -0700
committer ChromeOS Commit Bot <chromeos-commit-bot@chromium.org> 1505247464 +0000

UPSTREAM: Sanitize 'move_pages()' permission checks

The 'move_paghes()' system call was introduced long long ago with the
same permission checks as for sending a signal (except using
CAP_SYS_NICE instead of CAP_SYS_KILL for the overriding capability).

That turns out to not be a great choice - while the system call really
only moves physical page allocations around (and you need other
capabilities to do a lot of it), you can check the return value to map
out some the virtual address choices and defeat ASLR of a binary that
still shares your uid.

So change the access checks to the more common 'ptrace_may_access()'
model instead.

This tightens the access checks for the uid, and also effectively
changes the CAP_SYS_NICE check to CAP_SYS_PTRACE, but it's unlikely that
anybody really _uses_ this legacy system call any more (we hav ebetter
NUMA placement models these days), so I expect nobody to notice.

Famous last words.

BUG=chromium:762903
TEST=Build and run

Change-Id: Ie5c0299225b5e05a5da3c9e86d9275a28f073f44
Reported-by: Otto Ebeling <otto.ebeling@iki.fi>
Acked-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Guenter Roeck <groeck@chromium.org>
(cherry picked from commit 197e7e521384a23)
Reviewed-on: https://chromium-review.googlesource.com/664042