CVE-2023-53366 in Linux
Summary
by MITRE • 09/17/2025
In the Linux kernel, the following vulnerability has been resolved:
block: be a bit more careful in checking for NULL bdev while polling
Wei reports a crash with an application using polled IO:
PGD 14265e067 P4D 14265e067 PUD 47ec50067 PMD 0 Oops: 0000 [#1] SMP
CPU: 0 PID: 21915 Comm: iocore_0 Kdump: loaded Tainted: G S 5.12.0-0_fbk12_clang_7346_g1bb6f2e7058f #1 Hardware name: Wiwynn Delta Lake MP T8/Delta Lake-Class2, BIOS Y3DLM08 04/10/2022 RIP: 0010:bio_poll+0x25/0x200 Code: 0f 1f 44 00 00 0f 1f 44 00 00 55 41 57 41 56 41 55 41 54 53 48 83 ec 28 65 48 8b 04 25 28 00 00 00 48 89 44 24 20 48 8b 47 08 <48> 8b 80 70 02 00 00 4c 8b 70 50 8b 6f 34 31 db 83 fd ff 75 25 65 RSP: 0018:ffffc90005fafdf8 EFLAGS: 00010292 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 74b43cd65dd66600 RDX: 0000000000000003 RSI: ffffc90005fafe78 RDI: ffff8884b614e140 RBP: ffff88849964df78 R08: 0000000000000000 R09: 0000000000000008 R10: 0000000000000000 R11: 0000000000000000 R12: ffff88849964df00 R13: ffffc90005fafe78 R14: ffff888137d3c378 R15: 0000000000000001 FS: 00007fd195000640(0000) GS:ffff88903f400000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000270 CR3: 0000000466121001 CR4: 00000000007706f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 PKRU: 55555554 Call Trace: iocb_bio_iopoll+0x1d/0x30 io_do_iopoll+0xac/0x250 __se_sys_io_uring_enter+0x3c5/0x5a0 ? __x64_sys_write+0x89/0xd0 do_syscall_64+0x2d/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x94f225d Code: 24 cc 00 00 00 41 8b 84 24 d0 00 00 00 c1 e0 04 83 e0 10 41 09 c2 8b 33 8b 53 04 4c 8b 43 18 4c 63 4b 0c b8 aa 01 00 00 0f 05 <85> c0 0f 88 85 00 00 00 29 03 45 84 f6 0f 84 88 00 00 00 41 f6 c7 RSP: 002b:00007fd194ffcd88 EFLAGS: 00000202 ORIG_RAX: 00000000000001aa RAX: ffffffffffffffda RBX: 00007fd194ffcdc0 RCX: 00000000094f225d RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000007 RBP: 00007fd194ffcdb0 R08: 0000000000000000 R09: 0000000000000008 R10: 0000000000000001 R11: 0000000000000202 R12: 00007fd269d68030 R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000000000
which is due to bio->bi_bdev being NULL. This can happen if we have two tasks doing polled IO, and task B ends up completing IO from task A if they are sharing a poll queue. If task B completes the IO and puts the bio into our cache, then it can allocate that bio again before task A is done polling for it. As that would necessitate a preempt between the two tasks, it's enough to just be a bit more careful in checking for whether or not bio->bi_bdev is NULL.
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Analysis
by VulDB Data Team • 12/27/2025
The vulnerability identified as CVE-2023-53366 resides within the Linux kernel's block layer implementation, specifically affecting the bio_poll function that handles polled I/O operations. This flaw manifests as a kernel crash occurring when applications utilize polled I/O mechanisms, particularly in scenarios involving concurrent tasks sharing the same poll queue. The issue stems from inadequate NULL pointer validation for the block device reference within the bio structure, leading to a potential null pointer dereference that results in system instability and potential denial of service conditions.
The technical root cause of this vulnerability involves a race condition scenario where multiple tasks perform polled I/O operations and share poll queues. When task B completes I/O operations initiated by task A, it may place the bio structure into a cache system. Subsequently, task B can reallocate that same bio structure before task A has finished polling for its completion. This sequence creates a situation where bio->bi_bdev becomes NULL while the polling function attempts to access it, resulting in the kernel oops and system crash observed in the stack trace. The crash occurs at the bio_poll function where the kernel attempts to dereference a NULL pointer, specifically at offset 0x270 in the memory mapping.
This vulnerability directly relates to CWE-476, which addresses NULL pointer dereference conditions, and can be categorized under ATT&CK technique T1499.100, representing the exploitation of kernel vulnerabilities for system instability. The operational impact extends beyond simple system crashes, as this vulnerability can be exploited to cause denial of service conditions in systems relying heavily on polled I/O operations such as high-performance storage applications, database systems, and real-time processing environments. The vulnerability is particularly concerning in multi-threaded environments where I/O operations are frequently shared across different tasks or processes.
Mitigation strategies for this vulnerability involve implementing additional NULL pointer checks within the bio_poll function to ensure proper validation of the bio->bi_bdev field before attempting to access it. The fix requires careful consideration of the existing polling queue management logic to prevent race conditions while maintaining performance characteristics. System administrators should prioritize updating their kernel versions to include the patched implementation that addresses this specific NULL pointer dereference issue. Additionally, monitoring for unusual system crashes or I/O operation failures in applications using polled I/O mechanisms can help identify potential exploitation attempts. Organizations should also implement proper kernel security hardening measures and maintain up-to-date security patches to prevent exploitation of similar kernel-level vulnerabilities that could compromise system stability and availability.