linux-kernel - Re: [PATCH net-next] bnxt_en: fix accessing vnic

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Message-ID: <CACKFLikoY8RXL6zAZWV1YQ23KZJDrsF44WpDUB0Bq3GYaq2GkA@mail.gmail.com>
Date: Mon, 26 Feb 2024 08:26:58 -0800
From: Michael Chan <michael.chan@...adcom.com>
To: Alexander Lobakin <aleksander.lobakin@...el.com>
Cc: "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Somnath Kotur <somnath.kotur@...adcom.com>, Pavan Chebbi <pavan.chebbi@...adcom.com>, 
	Kalesh AP <kalesh-anakkur.purayil@...adcom.com>, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] bnxt_en: fix accessing vnic_info before
 allocating it

On Mon, Feb 26, 2024 at 6:51 AM Alexander Lobakin
<aleksander.lobakin@...el.com> wrote:
>
> bnxt_alloc_mem() dereferences ::vnic_info in the variable declaration
> block, but allocates it much later. As a result, the following crash
> happens on my setup:
>
>  BUG: kernel NULL pointer dereference, address: 0000000000000090
>  fbcon: Taking over console
>  #PF: supervisor write access in kernel mode
>  #PF: error_code (0x0002) - not-present page
>  PGD 12f382067 P4D 0
>  Oops: 8002 [#1] PREEMPT SMP NOPTI
>  CPU: 47 PID: 2516 Comm: NetworkManager Not tainted 6.8.0-rc5-libeth+ #49
>  Hardware name: Intel Corporation M50CYP2SBSTD/M58CYP2SBSTD, BIOS SE5C62086B.01.01.0088.2305172341 05/17/2023
>  RIP: 0010:bnxt_alloc_mem+0x1609/0x1910 [bnxt_en]
>  Code: 81 c8 48 83 c8 08 31 c9 e9 d7 fe ff ff c7 44 24 Oc 00 00 00 00 49 89 d5 e9 2d fe ff ff 41 89 c6 e9 88 00 00 00 48 8b 44 24 50 <80> 88 90 00 00 00 Od 8b 43 74 a8 02 75 1e f6 83 14 02 00 00 80 74
>  RSP: 0018:ff3f25580f3432c8 EFLAGS: 00010246
>  RAX: 0000000000000000 RBX: ff15a5cfc45249e0 RCX: 0000002079777000
>  RDX: ff15a5dfb9767000 RSI: 0000000000000000 RDI: 0000000000000000
>  RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
>  R10: ff15a5dfb9777000 R11: ffffff8000000000 R12: 0000000000000000
>  R13: 0000000000000000 R14: 0000000000000020 R15: ff15a5cfce34f540
>  FS:  000007fb9a160500(0000) GS:ff15a5dfbefc0000(0000) knlGS:0000000000000000
>  CS:  0010 DS: 0000 ES: 0000 CRO: 0000000080050033
>  CR2: 0000000000000090 CR3: 0000000109efc00Z CR4: 0000000000771ef0
>  DR0: 0000000000000000 DR1: 0000000000000000 DRZ: 0000000000000000
>  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>  PKRU: 55555554
>
>  Call Trace:
>  <TASK>
>  ? __die_body+0x68/0xb0
>  ? page_fault_oops+0x3a6/0x400
>  ? exc_page_fault+0x7a/0x1b0
>  ? asm_exc_page_fault+0x26/8x30
>  ? bnxt_alloc_mem+0x1609/0x1910 [bnxt_en]
>  ? bnxt_alloc_mem+0x1389/8x1918 [bnxt_en]
>  _bnxt_open_nic+0x198/0xa50 [bnxt_en]
>  ? bnxt_hurm_if_change+0x287/0x3d0 [bnxt_en]
>  bnxt_open+0xeb/0x1b0 [bnxt_en]
>  _dev_open+0x12e/0x1f0
>  _dev_change_flags+0xb0/0x200
>  dev_change_flags+0x25/0x60
>  do_setlink+0x463/0x1260
>  ? sock_def_readable+0x14/0xc0
>  ? rtnl_getlink+0x4b9/0x590
>  ? _nla_validate_parse+0x91/0xfa0
>  rtnl_newlink+0xbac/0xe40
>  <...>
>
> Don't create a variable and dereference the first array member directly
> since it's used only once in the code.
>
> Fixes: ef4ee64e9990 ("bnxt_en: Define BNXT_VNIC_DEFAULT for the default vnic index")
> Signed-off-by: Alexander Lobakin <aleksander.lobakin@...el.com>

Thanks.
Reviewed-by: Michael Chan <michael.chan@...adcom.com>

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