tjh.dev / kernel
Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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cxl/mbox: validate payload size before accessing contents in cxl_payload_from_user_allowed()

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.

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>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://patch.msgid.link/20260220001618.963490-2-dave@stgolabs.net
Signed-off-by: Dave Jiang <dave.jiang@intel.com>

authored by

Davidlohr Bueso and committed by
Dave Jiang 60b5d1f6 96a1fd0d

+9 -2
+9 -2
drivers/cxl/core/mbox.c
··· 311 311 * cxl_payload_from_user_allowed() - Check contents of in_payload. 312 312 * @opcode: The mailbox command opcode. 313 313 * @payload_in: Pointer to the input payload passed in from user space. 314 + * @in_size: Size of @payload_in in bytes. 314 315 * 315 316 * Return: 316 317 * * true - payload_in passes check for @opcode. ··· 326 325 * 327 326 * The specific checks are determined by the opcode. 328 327 */ 329 - static bool cxl_payload_from_user_allowed(u16 opcode, void *payload_in) 328 + static bool cxl_payload_from_user_allowed(u16 opcode, void *payload_in, 329 + size_t in_size) 330 330 { 331 331 switch (opcode) { 332 332 case CXL_MBOX_OP_SET_PARTITION_INFO: { 333 333 struct cxl_mbox_set_partition_info *pi = payload_in; 334 334 335 + if (in_size < sizeof(*pi)) 336 + return false; 335 337 if (pi->flags & CXL_SET_PARTITION_IMMEDIATE_FLAG) 336 338 return false; 337 339 break; ··· 342 338 case CXL_MBOX_OP_CLEAR_LOG: { 343 339 const uuid_t *uuid = (uuid_t *)payload_in; 344 340 341 + if (in_size < sizeof(uuid_t)) 342 + return false; 345 343 /* 346 344 * Restrict the ‘Clear log’ action to only apply to 347 345 * Vendor debug logs. ··· 371 365 if (IS_ERR(mbox_cmd->payload_in)) 372 366 return PTR_ERR(mbox_cmd->payload_in); 373 367 374 - if (!cxl_payload_from_user_allowed(opcode, mbox_cmd->payload_in)) { 368 + if (!cxl_payload_from_user_allowed(opcode, mbox_cmd->payload_in, 369 + in_size)) { 375 370 dev_dbg(cxl_mbox->host, "%s: input payload not allowed\n", 376 371 cxl_mem_opcode_to_name(opcode)); 377 372 kvfree(mbox_cmd->payload_in);