KASAN: null-ptr-deref Read in xprt_reserve

Status: upstream: reported on 2026/10/11 06:54
Subsystems: net nfs
Labels: prio:low
[Documentation on labels]
Reported-by: syzbot+ae55a0fac80c73c938ac@syzkaller.appspotmail.com
First crash: 4d19h, last: 2d12h
▶ ▼ ✨ AI Jobs (3)
ID Workflow Result Correct Bug Created Started Finished Revision
521cc15a repro-c 💥 KASAN: null-ptr-deref Read in xprt_reserve 2026/10/11 04:02 2026/10/11 04:02 2026/10/11 05:13 4f92358f
d8f532af repro-c 💥 KASAN: null-ptr-deref Read in xprt_reserve 2026/10/09 03:03 2026/10/09 03:03 2026/10/09 03:36 723be09b
f45b8831 assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ KASAN: null-ptr-deref Read in xprt_reserve 2026/10/08 00:00 2026/10/08 00:00 2026/10/08 01:02 f8f239cf
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [net?] [nfs?] KASAN: null-ptr-deref Read in xprt_reserve 0 (1) 2026/10/11 06:54

Sample crash report:
==================================================================
BUG: KASAN: null-ptr-deref in instrument_atomic_read include/linux/instrumented.h:82 [inline]
BUG: KASAN: null-ptr-deref in _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
BUG: KASAN: null-ptr-deref in xprt_throttle_congested net/sunrpc/xprt.c:1708 [inline]
BUG: KASAN: null-ptr-deref in xprt_reserve+0xe2/0x2c0 net/sunrpc/xprt.c:1948
Read of size 8 at addr 0000000000000628 by task syz.8.3118/20390

CPU: 1 UID: 0 PID: 20390 Comm: syz.8.3118 Tainted: G S           L      syzkaller #0 PREEMPT(full) 
Tainted: [S]=CPU_OUT_OF_SPEC, [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/26/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x264/0x2c0 mm/kasan/generic.c:200
 instrument_atomic_read include/linux/instrumented.h:82 [inline]
 _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
 xprt_throttle_congested net/sunrpc/xprt.c:1708 [inline]
 xprt_reserve+0xe2/0x2c0 net/sunrpc/xprt.c:1948
 __rpc_execute+0x526/0x1280 net/sunrpc/sched.c:947
 rpc_execute+0x1c1/0x390 net/sunrpc/sched.c:1023
 rpc_run_task+0x4a6/0x660 net/sunrpc/clnt.c:1269
 rpc_ping_noreply net/sunrpc/clnt.c:2944 [inline]
 rpc_create_xprt+0x452/0xa90 net/sunrpc/clnt.c:494
 rpc_create+0x649/0x900 net/sunrpc/clnt.c:619
 gssp_rpc_create net/sunrpc/auth_gss/gss_rpc_upcall.c:107 [inline]
 set_gssp_clnt+0x188/0x2d0 net/sunrpc/auth_gss/gss_rpc_upcall.c:131
 write_gssp+0x21e/0x310 net/sunrpc/auth_gss/svcauth_gss.c:1423
 pde_write fs/proc/inode.c:330 [inline]
 proc_reg_write+0x1e9/0x2e0 fs/proc/inode.c:342
 vfs_write+0x296/0xba0 fs/read_write.c:685
 ksys_write+0x150/0x270 fs/read_write.c:739
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f44e699e1d9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f44e78be028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f44e6c25fa0 RCX: 00007f44e699e1d9
RDX: 0000000000000001 RSI: 0000200000000300 RDI: 0000000000000005
RBP: 00007f44e6a35888 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f44e6c26038 R14: 00007f44e6c25fa0 R15: 00007ffdb88808e8
 </TASK>
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/09 04:40 upstream 6c377d19d4a5 b2734a59 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root KASAN: null-ptr-deref Read in xprt_reserve
2026/10/06 21:36 linux-next eea3fef32a9c f7710056 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root KASAN: null-ptr-deref Read in xprt_reserve
* Struck through repros no longer work on HEAD.