Re: [PATCH 3/3] mm: catch memory commitment underflow

Sasha Levin
2015-01-18T11:34:30Z

On 06/24/2014 04:16 PM, Konstantin Khlebnikov wrote:
> This patch prints warning (if CONFIG_DEBUG_VM=y) when
> memory commitment becomes too negative.
>
> Signed-off-by: Konstantin Khlebnikov <koct9i@gmail.com>

Hi Konstantin,

I seem to be hitting this warning when fuzzing on the latest -next kernel:

[ 683.674323] ------------[ cut here ]------------
[ 683.675552] WARNING: CPU: 12 PID: 25654 at mm/mmap.c:157 __vm_enough_memory+0x1b7/0x1d0()
[ 683.676972] memory commitment underflow
[ 683.678212] Modules linked in:
[ 683.678219] CPU: 12 PID: 25654 Comm: trinity-c373 Not tainted 3.19.0-rc4-next-20150116-sasha-00054-g4ad498c-dirty #1744
[ 683.678227] ffffffff9c6f7e73 ffff8802c0883a58 ffffffff9b439fb2 0000000000000000
[ 683.678231] ffff8802c0883aa8 ffff8802c0883a98 ffffffff98159e1a ffff8802c0883ae8
[ 683.678236] 0000000000000001 0000000000000000 ffffffffffff76f1 ffff8802a9749000
[ 683.678243] Call Trace:
[ 683.678288] dump_stack (lib/dump_stack.c:52)
[ 683.678297] warn_slowpath_common (kernel/panic.c:447)
[ 683.678302] warn_slowpath_fmt (kernel/panic.c:461)
[ 683.678307] __vm_enough_memory (mm/mmap.c:157 (discriminator 3))
[ 683.678317] cap_vm_enough_memory (security/commoncap.c:958)
[ 683.678323] security_vm_enough_memory_mm (security/security.c:212)
[ 683.678331] shmem_getpage_gfp (mm/shmem.c:1161)
[ 683.678337] shmem_write_begin (mm/shmem.c:1495)
[ 683.678343] generic_perform_write (mm/filemap.c:2491)
[ 683.678447] __generic_file_write_iter (mm/filemap.c:2632)
[ 683.678452] generic_file_write_iter (mm/filemap.c:2659)
[ 683.678458] do_iter_readv_writev (fs/read_write.c:680)
[ 683.678461] do_readv_writev (fs/read_write.c:848)
[ 683.678512] vfs_writev (fs/read_write.c:893)
[ 683.678515] SyS_writev (fs/read_write.c:926 fs/read_write.c:917)
[ 683.678520] tracesys_phase2 (arch/x86/kernel/entry_64.S:529)

Thanks,
Sasha