[PATCH] mm: Don't warn if memdup_user fails

Sasha Levin
2012-01-11T16:51:19Z

memdup_user() is called when we need to copy data from userspace. This
means that a user is able to trigger warnings if the kmalloc() inside
memdup_user() fails.

For example, this is one caused by writing to much data to ecryptdev:

[ 912.739685] ------------[ cut here ]------------
[ 912.745080] WARNING: at mm/page_alloc.c:2217 __alloc_pages_nodemask+0x22c/0x910()
[ 912.746525] Pid: 19977, comm: trinity Not tainted 3.2.0-next-20120110-sasha #120
[ 912.747915] Call Trace:
[ 912.748415] [<ffffffff8115ec5c>] ? __alloc_pages_nodemask+0x22c/0x910
[ 912.749651] [<ffffffff8109a2d5>] warn_slowpath_common+0x75/0xb0
[ 912.750756] [<ffffffff8109a3d5>] warn_slowpath_null+0x15/0x20
[ 912.751831] [<ffffffff8115ec5c>] __alloc_pages_nodemask+0x22c/0x910
[ 912.754230] [<ffffffff81070fd5>] ? pvclock_clocksource_read+0x55/0xd0
[ 912.755484] [<ffffffff8106ff56>] ? kvm_clock_read+0x46/0x80
[ 912.756565] [<ffffffff810d1548>] ? sched_clock_cpu+0xc8/0x140
[ 912.757667] [<ffffffff810cc731>] ? get_parent_ip+0x11/0x50
[ 912.758731] [<ffffffff810cc731>] ? get_parent_ip+0x11/0x50
[ 912.759890] [<ffffffff81341a4b>] ? ecryptfs_miscdev_write+0x6b/0x240
[ 912.761119] [<ffffffff81196c80>] alloc_pages_current+0xa0/0x110
[ 912.762269] [<ffffffff8115ba1f>] __get_free_pages+0xf/0x40
[ 912.763347] [<ffffffff811a6082>] __kmalloc_track_caller+0x172/0x190
[ 912.764561] [<ffffffff8116f0ab>] memdup_user+0x2b/0x90
[ 912.765526] [<ffffffff81341a4b>] ecryptfs_miscdev_write+0x6b/0x240
[ 912.766669] [<ffffffff813419e0>] ? ecryptfs_miscdev_open+0x190/0x190
[ 912.767832] [<ffffffff811ba360>] do_loop_readv_writev+0x50/0x80
[ 912.770735] [<ffffffff811ba69e>] do_readv_writev+0x1ce/0x1e0
[ 912.773059] [<ffffffff8251bbbc>] ? __mutex_unlock_slowpath+0x10c/0x200
[ 912.774634] [<ffffffff810cc731>] ? get_parent_ip+0x11/0x50
[ 912.775699] [<ffffffff810cc8dd>] ? sub_preempt_count+0x9d/0xd0
[ 912.776827] [<ffffffff8251f09d>] ? retint_swapgs+0x13/0x1b
[ 912.777887] [<ffffffff811ba758>] vfs_writev+0x48/0x60
[ 912.779162] [<ffffffff811ba86f>] sys_writev+0x4f/0xb0
[ 912.780152] [<ffffffff8251f979>] system_call_fastpath+0x16/0x1b
[ 912.793046] ---[ end trace 50c38c9cdee53379 ]---
[ 912.793906] ecryptfs_miscdev_write: memdup_user returned error [-12]

Failing memdup_user() shouldn't be generating warnings, instead it should
be notifying userspace about the error.

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
---
mm/util.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/mm/util.c b/mm/util.c
index 136ac4f..88bb4d4 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -91,7 +91,7 @@ void *memdup_user(const void __user *src, size_t len)
* cause pagefault, which makes it pointless to use GFP_NOFS
* or GFP_ATOMIC.
*/
- p = kmalloc_track_caller(len, GFP_KERNEL);
+ p = kmalloc_track_caller(len, GFP_KERNEL | __GFP_NOWARN);
if (!p)
return ERR_PTR(-ENOMEM);

--
1.7.8.3