CVE-2022-50674
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BaseFortify

Publication date: 2025-12-09

Last updated on: 2025-12-09

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: riscv: vdso: fix NULL deference in vdso_join_timens() when vfork Testing tools/testing/selftests/timens/vfork_exec.c got below kernel log: [ 6.838454] Unable to handle kernel access to user memory without uaccess routines at virtual address 0000000000000020 [ 6.842255] Oops [#1] [ 6.842871] Modules linked in: [ 6.844249] CPU: 1 PID: 64 Comm: vfork_exec Not tainted 6.0.0-rc3-rt15+ #8 [ 6.845861] Hardware name: riscv-virtio,qemu (DT) [ 6.848009] epc : vdso_join_timens+0xd2/0x110 [ 6.850097] ra : vdso_join_timens+0xd2/0x110 [ 6.851164] epc : ffffffff8000635c ra : ffffffff8000635c sp : ff6000000181fbf0 [ 6.852562] gp : ffffffff80cff648 tp : ff60000000fdb700 t0 : 3030303030303030 [ 6.853852] t1 : 0000000000000030 t2 : 3030303030303030 s0 : ff6000000181fc40 [ 6.854984] s1 : ff60000001e6c000 a0 : 0000000000000010 a1 : ffffffff8005654c [ 6.856221] a2 : 00000000ffffefff a3 : 0000000000000000 a4 : 0000000000000000 [ 6.858114] a5 : 0000000000000000 a6 : 0000000000000008 a7 : 0000000000000038 [ 6.859484] s2 : ff60000001e6c068 s3 : ff6000000108abb0 s4 : 0000000000000000 [ 6.860751] s5 : 0000000000001000 s6 : ffffffff8089dc40 s7 : ffffffff8089dc38 [ 6.862029] s8 : ffffffff8089dc30 s9 : ff60000000fdbe38 s10: 000000000000005e [ 6.863304] s11: ffffffff80cc3510 t3 : ffffffff80d1112f t4 : ffffffff80d1112f [ 6.864565] t5 : ffffffff80d11130 t6 : ff6000000181fa00 [ 6.865561] status: 0000000000000120 badaddr: 0000000000000020 cause: 000000000000000d [ 6.868046] [<ffffffff8008dc94>] timens_commit+0x38/0x11a [ 6.869089] [<ffffffff8008dde8>] timens_on_fork+0x72/0xb4 [ 6.870055] [<ffffffff80190096>] begin_new_exec+0x3c6/0x9f0 [ 6.871231] [<ffffffff801d826c>] load_elf_binary+0x628/0x1214 [ 6.872304] [<ffffffff8018ee7a>] bprm_execve+0x1f2/0x4e4 [ 6.873243] [<ffffffff8018f90c>] do_execveat_common+0x16e/0x1ee [ 6.874258] [<ffffffff8018f9c8>] sys_execve+0x3c/0x48 [ 6.875162] [<ffffffff80003556>] ret_from_syscall+0x0/0x2 [ 6.877484] ---[ end trace 0000000000000000 ]--- This is because the mm->context.vdso_info is NULL in vfork case. From another side, mm->context.vdso_info either points to vdso info for RV64 or vdso info for compat, there's no need to bloat riscv's mm_context_t, we can handle the difference when setup the additional page for vdso.
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Meta Information
Published
2025-12-09
Last Modified
2025-12-09
Generated
2026-05-07
AI Q&A
2025-12-09
EPSS Evaluated
2026-05-05
NVD
CVE-2022-50674
EUVD
EUVD-2022-55731
Affected Vendors & Products
Currently, no data is known.
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-UNKNOWN
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability is a NULL pointer dereference in the Linux kernel's riscv vdso_join_timens() function when using vfork. Specifically, the mm->context.vdso_info is NULL in the vfork case, which leads to a kernel crash (NULL dereference) when the function tries to access this NULL pointer. This issue was fixed by handling the vdso_info setup properly without bloating the riscv mm_context_t structure.


How can this vulnerability impact me? :

This vulnerability can cause the Linux kernel to crash or become unstable when a process uses vfork on riscv architecture, due to a NULL pointer dereference. This can lead to denial of service or system instability.


How can this vulnerability be detected on my network or system? Can you suggest some commands?

This vulnerability can be detected by monitoring the kernel logs for specific Oops messages related to vdso_join_timens() NULL dereference when using vfork. Look for kernel log entries similar to: "Unable to handle kernel access to user memory without uaccess routines at virtual address 0000000000000020" and "Oops [#1]" with references to vdso_join_timens in the stack trace. You can use the command 'dmesg | grep vdso_join_timens' or 'journalctl -k | grep vdso_join_timens' to find such logs.


What immediate steps should I take to mitigate this vulnerability?

Immediate mitigation involves updating the Linux kernel to a version where this vulnerability is fixed, as it is a kernel-level NULL pointer dereference issue in the riscv vdso code path. Until an update is applied, avoid using vfork on affected riscv systems to prevent triggering the bug.


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