CVE-2022-48751

In the Linux kernel, the following vulnerability has been resolved:

net/smc: Transitional solution for clcsock race issue

We encountered a crash in smc_setsockopt() and it is caused by accessing smc->clcsock after clcsock was released.

BUG: kernel NULL pointer dereference, address: 0000000000000020 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] PREEMPT SMP PTI CPU: 1 PID: 50309 Comm: nginx Kdump: loaded Tainted: G E 5.16.0-rc4+ #53 RIP: 0010:smc_setsockopt+0x59/0x280 [smc] Call Trace: __sys_setsockopt+0xfc/0x190 __x64_sys_setsockopt+0x20/0x30 do_syscall_64+0x34/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7f16ba83918e

This patch tries to fix it by holding clcsock_release_lock and checking whether clcsock has already been released before access.

In case that a crash of the same reason happens in smc_getsockopt() or smc_switch_to_fallback(), this patch also checkes smc->clcsock in them too. And the caller of smc_switch_to_fallback() will identify whether fallback succeeds according to the return value.

Weakness

A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/38f0bdd548fd2ef5d481b88d8a2bfef968452e34
• https://git.kernel.org/stable/c/4284225cd8001e134f5cf533a7cd244bbb654d0f
• https://git.kernel.org/stable/c/c0bf3d8a943b6f2e912b7c1de03e2ef28e76f760
• https://git.kernel.org/stable/c/38f0bdd548fd2ef5d481b88d8a2bfef968452e34
• https://git.kernel.org/stable/c/4284225cd8001e134f5cf533a7cd244bbb654d0f
• https://git.kernel.org/stable/c/c0bf3d8a943b6f2e912b7c1de03e2ef28e76f760