[PATCH bpf] xsk: silence warning on memory allocation failure

[PATCH bpf] xsk: silence warning on memory allocation failure

[Björn Töpel]

From: Björn Töpel <bjorn.topel@intel.com>

syzkaller reported a warning from xdp_umem_pin_pages():

  WARNING: CPU: 1 PID: 4537 at mm/slab_common.c:996 kmalloc_slab+0x56/0x70 mm/slab_common.c:996
  ...
  __do_kmalloc mm/slab.c:3713 [inline]
  __kmalloc+0x25/0x760 mm/slab.c:3727
  kmalloc_array include/linux/slab.h:634 [inline]
  kcalloc include/linux/slab.h:645 [inline]
  xdp_umem_pin_pages net/xdp/xdp_umem.c:205 [inline]
  xdp_umem_reg net/xdp/xdp_umem.c:318 [inline]
  xdp_umem_create+0x5c9/0x10f0 net/xdp/xdp_umem.c:349
  xsk_setsockopt+0x443/0x550 net/xdp/xsk.c:531
  __sys_setsockopt+0x1bd/0x390 net/socket.c:1935
  __do_sys_setsockopt net/socket.c:1946 [inline]
  __se_sys_setsockopt net/socket.c:1943 [inline]
  __x64_sys_setsockopt+0xbe/0x150 net/socket.c:1943
  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

This is a warning about attempting to allocate more than
KMALLOC_MAX_SIZE memory. The request originates from userspace, and if
the request is too big, the kernel is free to deny its allocation. In
this patch, the failed allocation attempt is silenced with
__GFP_NOWARN.

Fixes: c0c77d8fb787 ("xsk: add user memory registration support sockopt")
Reported-by: syzbot+4abadc5d69117b346506@syzkaller.appspotmail.com
Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
---
 net/xdp/xdp_umem.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c
index b9ef487c4618..f47abb46c587 100644
--- a/net/xdp/xdp_umem.c
+++ b/net/xdp/xdp_umem.c
@@ -204,7 +204,8 @@ static int xdp_umem_pin_pages(struct xdp_umem *umem)
 	long npgs;
 	int err;
 
-	umem->pgs = kcalloc(umem->npgs, sizeof(*umem->pgs), GFP_KERNEL);
+	umem->pgs = kcalloc(umem->npgs, sizeof(*umem->pgs),
+			    GFP_KERNEL | __GFP_NOWARN);
 	if (!umem->pgs)
 		return -ENOMEM;
 
-- 
2.14.1

Re: [PATCH bpf] xsk: silence warning on memory allocation failure

[Daniel Borkmann]

On 06/11/2018 01:57 PM, Björn Töpel wrote:
> From: Björn Töpel <bjorn.topel@intel.com>
> 
> syzkaller reported a warning from xdp_umem_pin_pages():
> 
>   WARNING: CPU: 1 PID: 4537 at mm/slab_common.c:996 kmalloc_slab+0x56/0x70 mm/slab_common.c:996
>   ...
>   __do_kmalloc mm/slab.c:3713 [inline]
>   __kmalloc+0x25/0x760 mm/slab.c:3727
>   kmalloc_array include/linux/slab.h:634 [inline]
>   kcalloc include/linux/slab.h:645 [inline]
>   xdp_umem_pin_pages net/xdp/xdp_umem.c:205 [inline]
>   xdp_umem_reg net/xdp/xdp_umem.c:318 [inline]
>   xdp_umem_create+0x5c9/0x10f0 net/xdp/xdp_umem.c:349
>   xsk_setsockopt+0x443/0x550 net/xdp/xsk.c:531
>   __sys_setsockopt+0x1bd/0x390 net/socket.c:1935
>   __do_sys_setsockopt net/socket.c:1946 [inline]
>   __se_sys_setsockopt net/socket.c:1943 [inline]
>   __x64_sys_setsockopt+0xbe/0x150 net/socket.c:1943
>   do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> This is a warning about attempting to allocate more than
> KMALLOC_MAX_SIZE memory. The request originates from userspace, and if
> the request is too big, the kernel is free to deny its allocation. In
> this patch, the failed allocation attempt is silenced with
> __GFP_NOWARN.
> 
> Fixes: c0c77d8fb787 ("xsk: add user memory registration support sockopt")
> Reported-by: syzbot+4abadc5d69117b346506@syzkaller.appspotmail.com
> Signed-off-by: Björn Töpel <bjorn.topel@intel.com>

Applied to bpf, thanks Björn!

Re: [PATCH bpf] xsk: silence warning on memory allocation failure

[Y Song]

On Mon, Jun 11, 2018 at 4:57 AM, Björn Töpel <bjorn.topel@gmail.com> wrote:
> From: Björn Töpel <bjorn.topel@intel.com>
>
> syzkaller reported a warning from xdp_umem_pin_pages():
>
>   WARNING: CPU: 1 PID: 4537 at mm/slab_common.c:996 kmalloc_slab+0x56/0x70 mm/slab_common.c:996
>   ...
>   __do_kmalloc mm/slab.c:3713 [inline]
>   __kmalloc+0x25/0x760 mm/slab.c:3727
>   kmalloc_array include/linux/slab.h:634 [inline]
>   kcalloc include/linux/slab.h:645 [inline]
>   xdp_umem_pin_pages net/xdp/xdp_umem.c:205 [inline]
>   xdp_umem_reg net/xdp/xdp_umem.c:318 [inline]
>   xdp_umem_create+0x5c9/0x10f0 net/xdp/xdp_umem.c:349
>   xsk_setsockopt+0x443/0x550 net/xdp/xsk.c:531
>   __sys_setsockopt+0x1bd/0x390 net/socket.c:1935
>   __do_sys_setsockopt net/socket.c:1946 [inline]
>   __se_sys_setsockopt net/socket.c:1943 [inline]
>   __x64_sys_setsockopt+0xbe/0x150 net/socket.c:1943
>   do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> This is a warning about attempting to allocate more than
> KMALLOC_MAX_SIZE memory. The request originates from userspace, and if
> the request is too big, the kernel is free to deny its allocation. In
> this patch, the failed allocation attempt is silenced with
> __GFP_NOWARN.
>
> Fixes: c0c77d8fb787 ("xsk: add user memory registration support sockopt")
> Reported-by: syzbot+4abadc5d69117b346506@syzkaller.appspotmail.com
> Signed-off-by: Björn Töpel <bjorn.topel@intel.com>

Acked-by: Yonghong Song <yhs@fb.com>