Messages in this thread Patch in this message | | | Date | Thu, 29 Mar 2012 14:09:34 -0700 | From | Andrew Morton <> | Subject | Re: suppress page allocation failure warnings from sys_listxattr |
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On Wed, 28 Mar 2012 23:00:00 -0400 Dave Jones <davej@redhat.com> wrote:
> On Wed, Mar 28, 2012 at 07:28:04PM -0700, Andrew Morton wrote: > > > But it looks like > > > key_add (see other thread from this evening) and probably others can be > > > called as a user and gobble up vmalloc space. omnomnom. > > > > hm, the keys code appears to prevent the user from reserving more than > > 20000 bytes of memory total (key_payload_reserve()), so it doesn't look > > very useful for screwing up vmalloc(). > > Then how did I trick it into trying an order 8 allocation ? > > trinity: page allocation failure: order:8, mode:0x40d0 > Pid: 27119, comm: trinity Not tainted 3.3.0+ #31 > Call Trace: > [<ffffffff8115dd66>] warn_alloc_failed+0xf6/0x160 > [<ffffffff816ad436>] ? __alloc_pages_direct_compact+0x1d0/0x1e2 > [<ffffffff81162492>] __alloc_pages_nodemask+0x8b2/0xb10 > [<ffffffff8119dae6>] alloc_pages_current+0xb6/0x120 > [<ffffffff8115d3b4>] __get_free_pages+0x14/0x50 > [<ffffffff811ac64f>] kmalloc_order_trace+0x3f/0x1a0 > [<ffffffff811aca0a>] __kmalloc+0x25a/0x280 > [<ffffffff812c034a>] sys_add_key+0x9a/0x210 > [<ffffffff813386be>] ? trace_hardirqs_on_thunk+0x3a/0x3f > [<ffffffff816c04e9>] system_call_fastpath+0x16/0x1b
Ah, that's different. The memory at *payload doesn't live beyond the syscall so it can't be used to cause vmalloc fragmentation.
We should squish the warning:
From: Andrew Morton <akpm@linux-foundation.org> Subject: security/keys/keyctl.c: suppress memory allocation failure warning
This allocation may be large. The code is probing to see if it will succeed and if not, it falls back to vmalloc(). We should suppress any page-allocation failure messages when the fallback happens.
Reported-by: Dave Jones <davej@redhat.com> Cc: David Howells <dhowells@redhat.com> Cc: James Morris <jmorris@namei.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> ---
security/keys/keyctl.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff -puN security/keys/keyctl.c~security-keys-keyctlc-suppress-memory-allocation-failure-warning security/keys/keyctl.c --- a/security/keys/keyctl.c~security-keys-keyctlc-suppress-memory-allocation-failure-warning +++ a/security/keys/keyctl.c @@ -84,7 +84,7 @@ SYSCALL_DEFINE5(add_key, const char __us vm = false; if (_payload) { ret = -ENOMEM; - payload = kmalloc(plen, GFP_KERNEL); + payload = kmalloc(plen, GFP_KERNEL | __GFP_NOWARN); if (!payload) { if (plen <= PAGE_SIZE) goto error2; _
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