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Subject[PATCH v2] pipe: Fail cleanly when root tries F_SETPIPE_SZ with big size
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When a user with the CAP_SYS_RESOURCE cap tries to F_SETPIPE_SZ a pipe with
size bigger than what kmalloc() can alloc it spits out an ugly warning:

[ 3.651552] ------------[ cut here ]------------
[ 3.652644] WARNING: at mm/page_alloc.c:2095 __alloc_pages_nodemask+0x5d3/0x7a0()
[ 3.654313] Pid: 733, comm: a.out Not tainted 3.2.0-rc1+ #4
[ 3.655568] Call Trace:
[ 3.656207] [<ffffffff810de163>] ? __alloc_pages_nodemask+0x5d3/0x7a0
[ 3.657698] [<ffffffff8107a575>] warn_slowpath_common+0x75/0xb0
[ 3.659018] [<ffffffff8107a675>] warn_slowpath_null+0x15/0x20
[ 3.660468] [<ffffffff810de163>] __alloc_pages_nodemask+0x5d3/0x7a0
[ 3.665725] [<ffffffff810f5432>] ? handle_pte_fault+0xf2/0x200
[ 3.667032] [<ffffffff8167b849>] ? _raw_spin_unlock+0x9/0x40
[ 3.668283] [<ffffffff810f2d76>] ? __pte_alloc+0x96/0x150
[ 3.669354] [<ffffffff81121121>] ? get_empty_filp+0x91/0x160
[ 3.670238] [<ffffffff810f6764>] ? handle_mm_fault+0x1a4/0x360
[ 3.671139] [<ffffffff810de342>] __get_free_pages+0x12/0x50
[ 3.671972] [<ffffffff811169fb>] __kmalloc+0x12b/0x150
[ 3.672782] [<ffffffff811283f5>] pipe_set_size+0x75/0x120
[ 3.673681] [<ffffffff81129998>] pipe_fcntl+0xf8/0x140
[ 3.674833] [<ffffffff81130264>] do_fcntl+0x2d4/0x410
[ 3.675960] [<ffffffff81129722>] ? do_pipe_flags+0xb2/0x100
[ 3.677218] [<ffffffff81130406>] sys_fcntl+0x66/0xa0
[ 3.678037] [<ffffffff8167c612>] system_call_fastpath+0x16/0x1b
[ 3.679008] ---[ end trace 432f702e6db7b5ee ]---

Instead, make kcalloc() handle the overflow case and fail quietly.

Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
---
fs/pipe.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/fs/pipe.c b/fs/pipe.c
index 4065f07..3e38dc6 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -1137,7 +1137,7 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long nr_pages)
if (nr_pages < pipe->nrbufs)
return -EBUSY;

- bufs = kcalloc(nr_pages, sizeof(struct pipe_buffer), GFP_KERNEL);
+ bufs = kcalloc(nr_pages, sizeof(struct pipe_buffer), GFP_KERNEL | __GFP_NOWARN);
if (unlikely(!bufs))
return -ENOMEM;

--
1.7.8.rc1


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