nfsd: clear acl_access/acl_default after releasing them

Summary

In the Linux kernel, the following vulnerability has been resolved: nfsd: clear acl_access/acl_default after releasing them If getting acl_default fails, acl_access and acl_default will be released simultaneously. However, acl_access will still retain a pointer pointing to the released posix_acl, which will trigger a WARNING in nfs3svc_release_getacl like this: ------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 26 PID: 3199 at lib/refcount.c:28 refcount_warn_saturate+0xb5/0x170 Modules linked in: CPU: 26 UID: 0 PID: 3199 Comm: nfsd Not tainted 6.12.0-rc6-00079-g04ae226af01f-dirty #8 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014 RIP: 0010:refcount_warn_saturate+0xb5/0x170 Code: cc cc 0f b6 1d b3 20 a5 03 80 fb 01 0f 87 65 48 d8 00 83 e3 01 75 e4 48 c7 c7 c0 3b 9b 85 c6 05 97 20 a5 03 01 e8 fb 3e 30 ff <0f> 0b eb cd 0f b6 1d 8a3 RSP: 0018:ffffc90008637cd8 EFLAGS: 00010282 RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff83904fde RDX: dffffc0000000000 RSI: 0000000000000008 RDI: ffff88871ed36380 RBP: ffff888158beeb40 R08: 0000000000000001 R09: fffff520010c6f56 R10: ffffc90008637ab7 R11: 0000000000000001 R12: 0000000000000001 R13: ffff888140e77400 R14: ffff888140e77408 R15: ffffffff858b42c0 FS: 0000000000000000(0000) GS:ffff88871ed00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000562384d32158 CR3: 000000055cc6a000 CR4: 00000000000006f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> ? refcount_warn_saturate+0xb5/0x170 ? __warn+0xa5/0x140 ? refcount_warn_saturate+0xb5/0x170 ? report_bug+0x1b1/0x1e0 ? handle_bug+0x53/0xa0 ? exc_invalid_op+0x17/0x40 ? asm_exc_invalid_op+0x1a/0x20 ? tick_nohz_tick_stopped+0x1e/0x40 ? refcount_warn_saturate+0xb5/0x170 ? refcount_warn_saturate+0xb5/0x170 nfs3svc_release_getacl+0xc9/0xe0 svc_process_common+0x5db/0xb60 ? __pfx_svc_process_common+0x10/0x10 ? __rcu_read_unlock+0x69/0xa0 ? __pfx_nfsd_dispatch+0x10/0x10 ? svc_xprt_received+0xa1/0x120 ? xdr_init_decode+0x11d/0x190 svc_process+0x2a7/0x330 svc_handle_xprt+0x69d/0x940 svc_recv+0x180/0x2d0 nfsd+0x168/0x200 ? __pfx_nfsd+0x10/0x10 kthread+0x1a2/0x1e0 ? kthread+0xf4/0x1e0 ? __pfx_kthread+0x10/0x10 ret_from_fork+0x34/0x60 ? __pfx_kthread+0x10/0x10 ret_from_fork_asm+0x1a/0x30 </TASK> Kernel panic - not syncing: kernel: panic_on_warn set ... Clear acl_access/acl_default after posix_acl_release is called to prevent UAF from being triggered.

Timeline

1. Feb 27, 2025, 2:18 AM UTCCVE published
2. Feb 27, 2025, 5:57 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: total

3. Oct 15, 2026, 1:04 AM UTCRecord last updated

Affected versions

• Linux Linux

  From a257cdd0e2179630d3201c32ba14d7fcb3c3a055 · fixed in 8a1737ae42c928384ab6447f6ee1a882510e85fa; From a257cdd0e2179630d3201c32ba14d7fcb3c3a055 · fixed in 6f7cfee1a316891890c505563aa54f3476db52fd; From a257cdd0e2179630d3201c32ba14d7fcb3c3a055 · fixed in 2e59b2b68782519560b3d6a41dd66a3d01a01cd3; From a257cdd0e2179630d3201c32ba14d7fcb3c3a055 · fixed in 55d947315fb5f67a35e4e1d3e01bb886b9c6decf; From a257cdd0e2179630d3201c32ba14d7fcb3c3a055 · fixed in f8d871523142f7895f250a856f8c4a4181614510; From a257cdd0e2179630d3201c32ba14d7fcb3c3a055 · fixed in 1fd94884174bd20beb1773990fd3b1aa877688d9; From a257cdd0e2179630d3201c32ba14d7fcb3c3a055 · fixed in 7faf14a7b0366f153284db0ad3347c457ea70136

• Linux Linux

  2.6.13

• KernelLinux

  From 2.6.13 · fixed in 5.10.235; From 5.11.0 · fixed in 5.15.179; From 5.16.0 · fixed in 6.1.129; From 6.2.0 · fixed in 6.6.79; From 6.7.0 · fixed in 6.12.16; From 6.13.0 · fixed in 6.13.4

References 7