CVE-2026-23297

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

nfsd: Fix cred ref leak in nfsd_nl_threads_set_doit().

syzbot reported memory leak of struct cred. [0]

nfsd_nl_threads_set_doit() passes get_current_cred() to nfsd_svc(), but put_cred() is not called after that.

The cred is finally passed down to _svc_xprt_create(), which calls get_cred() with the cred for struct svc_xprt.

The ownership of the refcount by get_current_cred() is not transferred to anywhere and is just leaked.

nfsd_svc() is also called from write_threads(), but it does not bump file->f_cred there.

nfsd_nl_threads_set_doit() is called from sendmsg() and current->cred does not go away.

Lets use current_cred() in nfsd_nl_threads_set_doit().

[0]: BUG: memory leak unreferenced object 0xffff888108b89480 (size 184): comm syz-executor, pid 5994, jiffies 4294943386 hex dump (first 32 bytes): 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ……………. 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ……………. backtrace (crc 369454a7): kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline] slab_post_alloc_hook mm/slub.c:4958 [inline] slab_alloc_node mm/slub.c:5263 [inline] kmem_cache_alloc_noprof+0x412/0x580 mm/slub.c:5270 prepare_creds+0x22/0x600 kernel/cred.c:185 copy_creds+0x44/0x290 kernel/cred.c:286 copy_process+0x7a7/0x2870 kernel/fork.c:2086 kernel_clone+0xac/0x6e0 kernel/fork.c:2651 __do_sys_clone+0x7f/0xb0 kernel/fork.c:2792 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xa4/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Weakness

The product does not sufficiently track and release allocated memory after it has been used, making the memory unavailable for reallocation and reuse.

Affected Software

Potential Mitigations

• Choose a language or tool that provides automatic memory management, or makes manual memory management less error-prone.
• For example, glibc in Linux provides protection against free of invalid pointers.
• When using Xcode to target OS X or iOS, enable automatic reference counting (ARC) [REF-391].
• To help correctly and consistently manage memory when programming in C++, consider using a smart pointer class such as std::auto_ptr (defined by ISO/IEC ISO/IEC 14882:2003), std::shared_ptr and std::unique_ptr (specified by an upcoming revision of the C++ standard, informally referred to as C++ 1x), or equivalent solutions such as Boost.

References

• https://git.kernel.org/stable/c/1cb968a2013ffa8112d52ebe605009ea1c6a582c
• https://git.kernel.org/stable/c/27c13c5bb0948e3b5c64e59f8a903231896fab9b
• https://git.kernel.org/stable/c/41170716421c25cd20b39e83f0e0762e212b377b
• https://git.kernel.org/stable/c/a3f88e3e18b51a7f654189189c762ebcdeaa7e29