Re: [PATCH] net/mlx5: fix a -Wstringop-truncation warning

[Saeed Mahameed <saeedm@mellanox.com>]

On Tue, 2019-08-27 at 16:12 -0400, Qian Cai wrote:
> On Mon, 2019-08-26 at 21:11 +0000, Saeed Mahameed wrote:
> > On Fri, 2019-08-23 at 15:56 -0400, Qian Cai wrote:
> > > In file included from ./arch/powerpc/include/asm/paca.h:15,
> > >                  from ./arch/powerpc/include/asm/current.h:13,
> > >                  from ./include/linux/thread_info.h:21,
> > >                  from ./include/asm-generic/preempt.h:5,
> > >                  from
> > > ./arch/powerpc/include/generated/asm/preempt.h:1,
> > >                  from ./include/linux/preempt.h:78,
> > >                  from ./include/linux/spinlock.h:51,
> > >                  from ./include/linux/wait.h:9,
> > >                  from ./include/linux/completion.h:12,
> > >                  from ./include/linux/mlx5/driver.h:37,
> > >                  from
> > > drivers/net/ethernet/mellanox/mlx5/core/lib/eq.h:6,
> > >                  from
> > > drivers/net/ethernet/mellanox/mlx5/core/diag/fw_tracer.c:33:
> > > In function 'strncpy',
> > >     inlined from 'mlx5_fw_tracer_save_trace' at
> > > drivers/net/ethernet/mellanox/mlx5/core/diag/fw_tracer.c:549:2,
> > >     inlined from 'mlx5_tracer_print_trace' at
> > > drivers/net/ethernet/mellanox/mlx5/core/diag/fw_tracer.c:574:2:
> > > ./include/linux/string.h:305:9: warning: '__builtin_strncpy'
> > > output
> > > may
> > > be truncated copying 256 bytes from a string of length 511
> > > [-Wstringop-truncation]
> > >   return __builtin_strncpy(p, q, size);
> > >          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > 
> > > Fix it by using the new strscpy_pad() since the commit
> > > 458a3bf82df4
> > > ("lib/string: Add strscpy_pad() function") which will always
> > > NUL-terminate the string, and avoid possibly leak data through
> > > the
> > > ring
> > > buffer where non-admin account might enable these events through
> > > perf.
> > > 
> > > Fixes: fd1483fe1f9f ("net/mlx5: Add support for FW reporter
> > > dump")
> > > Signed-off-by: Qian Cai <cai@lca.pw>
> > 
> > Hi Qian and thanks for your patch,
> > 
> > We already have a patch that handles this issue, please check it
> > out:
> > https://git.kernel.org/pub/scm/linux/kernel/git/saeed/linux.git/commit/?h=net-
> > next-mlx5
> > 
> 
> That commit will make "struct mlx5_fw_tracer" too large and trigger a
> warning in
> __alloc_pages_nodemask(),
> 

I see! thanks for the input, the patch is still under review and not
yet passed to regression queue.

I will take your patch.. and will fix our patch on top of yours.

>         /*
>          * There are several places where we assume that the order
> value is sane
>          * so bail out early if the request is out of bound.
>          */
>         if (unlikely(order >= MAX_ORDER)) {
>                 WARN_ON_ONCE(!(gfp_mask & __GFP_NOWARN));
>                 return NULL;
>         }
> 
> [   98.339576][  T914] WARNING: CPU: 0 PID: 914 at
> mm/page_alloc.c:4705
> __alloc_pages_nodemask+0x441/0x1bb0
> [   98.349174][  T914] Modules linked in: smartpqi(+)
> scsi_transport_sas tg3
> mlx5_core(+) libphy firmware_class dm_mirror dm_region_hash dm_log
> dm_mod
> efivarfs
> [   98.363495][  T914] CPU: 0 PID: 914 Comm: kworker/0:2 Not tainted
> 5.3.0-rc6-
> next-20190827+ #14
> [   98.372243][  T914] Hardware name: HPE ProLiant DL385
> Gen10/ProLiant DL385
> Gen10, BIOS A40 07/10/2019
> [   98.381627][  T914] Workqueue: events work_for_cpu_fn
> [   98.386720][  T914] RIP: 0010:__alloc_pages_nodemask+0x441/0x1bb0
> [   98.392917][  T914] Code: 17 00 00 48 8d 65 d8 5b 41 5c 41 5d 41
> 5e 41 5f 5d
> c3 89 85 3c fe ff ff bb 01 00 00 00 e9 96 fd ff ff 81 e7 00 20 00 00
> 75 02 <0f>
> 0b 48 c7 85 50 fe ff ff 00 00 00 00 eb 82 31 d2 be 36 12 00 00
> [   98.412740][  T914] RSP: 0018:ffff88853418f948 EFLAGS: 00010246
> [   98.418704][  T914] RAX: 0000000000000000 RBX: ffffffff9571a860
> RCX:
> 1ffff110a6831f3e
> [   98.426652][  T914] RDX: 0000000000000000 RSI: 000000000000000b
> RDI:
> 0000000000000000
> [   98.434661][  T914] RBP: ffff88853418fb58 R08: ffffed1108808465
> R09:
> ffffed1108808465
> [   98.442613][  T914] R10: ffffed1108808464 R11: ffff888844042323
> R12:
> 0000000000000000
> [   98.450548][  T914] R13: 000000000000000b R14: 0000000000000000
> R15:
> 0000000000000001
> [   98.458434][  T914] FS:  0000000000000000(0000)
> GS:ffff888844000000(0000)
> knlGS:0000000000000000
> [   98.467350][  T914] CS:  0010 DS: 0000 ES: 0000 CR0:
> 0000000080050033
> [   98.473911][  T914] CR2: 0000555c64680148 CR3: 0000000550412000
> CR4:
> 00000000003406b0
> [   98.481838][  T914] Call Trace:
> [   98.485011][  T914]  ? find_next_bit+0x2c/0xa0
> [   98.489490][  T914]  ? __kasan_check_write+0x14/0x20
> [   98.494506][  T914]  ? graph_lock+0xb8/0x120
> [   98.498811][  T914]  ? __free_zapped_classes+0x740/0x740
> [   98.504239][  T914]  ? gfp_pfmemalloc_allowed+0xc0/0xc0
> [   98.509504][  T914]  ? __kasan_check_read+0x11/0x20
> [   98.514443][  T914]  ? register_lock_class+0x5ef/0x960
> [   98.519624][  T914]  ? rcu_read_lock_sched_held+0xac/0xe0
> [   98.525152][  T914]  ? rcu_read_lock_any_held.part.5+0x20/0x20
> [   98.531130][  T914]  ? find_next_bit+0x2c/0xa0
> [   98.535610][  T914]  alloc_pages_current+0x9c/0x110
> [   98.540638][  T914]  kmalloc_order+0x22/0x70
> [   98.544943][  T914]  kmalloc_order_trace+0x23/0x100
> [   98.550072][  T914]  mlx5_fw_tracer_create+0x51/0x870 [mlx5_core]
> [   98.556213][  T914]  ? __mutex_init+0x94/0xa0
> [   98.560744][  T914]  ? mlx5_init_rl_table+0x144/0x210 [mlx5_core]
> [   98.566929][  T914]  mlx5_load_one+0x199/0x980 [mlx5_core]
> [   98.572637][  T914]  init_one+0x494/0x760 [mlx5_core]
> [   98.577771][  T914]  ? mlx5_pci_resume+0xd0/0xd0 [mlx5_core]
> [   98.583574][  T914]  local_pci_probe+0x7a/0xc0
> [   98.588054][  T914]  ? pci_dma_configure+0xa0/0xa0
> [   98.592938][  T914]  work_for_cpu_fn+0x2e/0x50
> [   98.597416][  T914]  process_one_work+0x53b/0xa70
> [   98.602220][  T914]  ? pwq_dec_nr_in_flight+0x170/0x170
> [   98.607485][  T914]  ? move_linked_works+0x113/0x150
> [   98.612497][  T914]  worker_thread+0x363/0x5b0
> [   98.616976][  T914]  kthread+0x1df/0x200
> [   98.620932][  T914]  ? process_one_work+0xa70/0xa70
> [   98.625847][  T914]  ? kthread_park+0xd0/0xd0
> [   98.630240][  T914]  ret_from_fork+0x22/0x40