From: Alison Schofield <alison.schofield@intel.com>
To: Davidlohr Bueso <dave@stgolabs.net>
Cc: <dave.jiang@intel.com>, <jonathan.cameron@huawei.com>,
<vishal.l.verma@intel.com>, <ira.weiny@intel.com>,
<dan.j.williams@intel.com>, <linux-cxl@vger.kernel.org>
Subject: Re: [PATCH 1/2] cxl/mbox: validate payload size before accessing contents in cxl_payload_from_user_allowed()
Date: Mon, 23 Feb 2026 11:23:24 -0800 [thread overview]
Message-ID: <aZypLDJLdhqfpTHn@aschofie-mobl2.lan> (raw)
In-Reply-To: <20260220001618.963490-2-dave@stgolabs.net>
On Thu, Feb 19, 2026 at 04:16:17PM -0800, Davidlohr Bueso wrote:
> cxl_payload_from_user_allowed() casts and dereferences the input
> payload without first verifying its size. When a raw mailbox command
> is sent with an undersized payload (ie: 1 byte for CXL_MBOX_OP_CLEAR_LOG,
> which expects a 16-byte UUID), uuid_equal() reads past the allocated buffer,
> triggering a KASAN splat:
>
> BUG: KASAN: slab-out-of-bounds in memcmp+0x176/0x1d0 lib/string.c:683
> Read of size 8 at addr ffff88810130f5c0 by task syz.1.62/2258
>
> CPU: 2 UID: 0 PID: 2258 Comm: syz.1.62 Not tainted 6.19.0-dirty #3 PREEMPT(voluntary)
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.17.0-0-gb52ca86e094d-prebuilt.qemu.org 04/01/2014
> Call Trace:
> <TASK>
> __dump_stack lib/dump_stack.c:94 [inline]
> dump_stack_lvl+0xab/0xe0 lib/dump_stack.c:120
> print_address_description mm/kasan/report.c:378 [inline]
> print_report+0xce/0x650 mm/kasan/report.c:482
> kasan_report+0xce/0x100 mm/kasan/report.c:595
> memcmp+0x176/0x1d0 lib/string.c:683
> uuid_equal include/linux/uuid.h:73 [inline]
> cxl_payload_from_user_allowed drivers/cxl/core/mbox.c:345 [inline]
> cxl_mbox_cmd_ctor drivers/cxl/core/mbox.c:368 [inline]
> cxl_validate_cmd_from_user drivers/cxl/core/mbox.c:522 [inline]
> cxl_send_cmd+0x9c0/0xb50 drivers/cxl/core/mbox.c:643
> __cxl_memdev_ioctl drivers/cxl/core/memdev.c:698 [inline]
> cxl_memdev_ioctl+0x14f/0x190 drivers/cxl/core/memdev.c:713
> vfs_ioctl fs/ioctl.c:51 [inline]
> __do_sys_ioctl fs/ioctl.c:597 [inline]
> __se_sys_ioctl fs/ioctl.c:583 [inline]
> __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> do_syscall_64+0xa8/0x330 arch/x86/entry/syscall_64.c:94
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7fdaf331ba79
> Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007fdaf1d77038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 00007fdaf3585fa0 RCX: 00007fdaf331ba79
> RDX: 00002000000001c0 RSI: 00000000c030ce02 RDI: 0000000000000003
> RBP: 00007fdaf33749df R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007fdaf3586038 R14: 00007fdaf3585fa0 R15: 00007ffced2af768
> </TASK>
>
> Add 'in_size' parameter to cxl_payload_from_user_allowed() and validate
> the payload is large enough.
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
>
> Fixes: 6179045ccc0c ("cxl/mbox: Block immediate mode in SET_PARTITION_INFO command")
> Fixes: 206f9fa9d555 ("cxl/mbox: Add Clear Log mailbox command")
> Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
snip
next prev parent reply other threads:[~2026-02-23 19:23 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-20 0:16 [PATCH 0/2] cxl/mbox: fix undersized payload handling in cxl_payload_from_user_allowed() Davidlohr Bueso
2026-02-20 0:16 ` [PATCH 1/2] cxl/mbox: validate payload size before accessing contents " Davidlohr Bueso
2026-02-23 19:23 ` Alison Schofield [this message]
2026-02-23 22:39 ` Dave Jiang
2026-02-20 0:16 ` [PATCH 2/2] cxl/mbox: return appropriate error " Davidlohr Bueso
2026-02-20 22:14 ` Alison Schofield
2026-02-21 18:55 ` Davidlohr Bueso
2026-02-23 19:27 ` Alison Schofield
2026-02-23 22:40 ` Dave Jiang
2026-02-27 13:38 ` Jonathan Cameron
2026-02-20 17:23 ` [PATCH 0/2] cxl/mbox: fix undersized payload handling " Dave Jiang
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