On 05.09.25 15:28, David Hildenbrand wrote:
On 05.09.25 15:07, David Hildenbrand wrote:
On 05.09.25 14:55, Eric Dumazet wrote:
On Fri, Sep 5, 2025 at 2:30 AM Naresh Kamboju naresh.kamboju@linaro.org wrote:
The following kernel crash was noticed on x86_64 running selftests net udpgso_bench.sh on Linux next-20250905 tag.
Regression Analysis:
- New regression? yes
- Reproducibility? Re-validation is in progress
First seen on next-20250905 Bad: next-20250905 Good: next-20250904
Test regression: next-20250905 x86_64 selftests net BUG kernel NULL pointer dereference zerocopy_fill_skb_from_iter
Reported-by: Linux Kernel Functional Testing lkft@linaro.org
x86_64: Test: * selftests: net: udpgso_bench.sh
Test error: selftests: net: udpgso_bench.sh ipv4 tcp
<trim>
# tcp zerocopy [ 991.110488] SELinux: unrecognized netlink message: protocol=4 nlmsg_type=19 sclass=netlink_tcpdiag_socket pid=64835 comm=ss # RTNETLINK answers: Invalid argument [ 991.129878] BUG: kernel NULL pointer dereference, address: 0000000000000008 [ 991.136850] #PF: supervisor read access in kernel mode [ 991.141986] #PF: error_code(0x0000) - not-present page [ 991.147118] PGD 0 P4D 0 [ 991.149657] Oops: Oops: 0000 [#1] SMP PTI [ 991.153661] CPU: 0 UID: 0 PID: 64842 Comm: udpgso_bench_tx Tainted: G S 6.17.0-rc4-next-20250905 #1 PREEMPT(voluntary) [ 991.165907] Tainted: [S]=CPU_OUT_OF_SPEC [ 991.169825] Hardware name: Supermicro SYS-5019S-ML/X11SSH-F, BIOS 2.7 12/07/2021 [ 991.177209] RIP: 0010:zerocopy_fill_skb_from_iter (include/linux/page-flags.h:284) [ 991.182954] Code: 4d 85 c0 0f 84 04 01 00 00 44 39 c7 41 0f 4d f8 4c 63 de 4a 8b 54 dc 30 49 89 d6 4d 29 ce 49 c1 fe 06 49 d3 ee 4d 85 f6 74 24 <48> 8b 4a 08 f6 c1 01 0f 85 cb 00 00 00 0f 1f 44 00 00 31 c9 48 f7 All code ======== 0: 4d 85 c0 test %r8,%r8 3: 0f 84 04 01 00 00 je 0x10d 9: 44 39 c7 cmp %r8d,%edi c: 41 0f 4d f8 cmovge %r8d,%edi 10: 4c 63 de movslq %esi,%r11 13: 4a 8b 54 dc 30 mov 0x30(%rsp,%r11,8),%rdx 18: 49 89 d6 mov %rdx,%r14 1b: 4d 29 ce sub %r9,%r14 1e: 49 c1 fe 06 sar $0x6,%r14 22: 49 d3 ee shr %cl,%r14 25: 4d 85 f6 test %r14,%r14 28: 74 24 je 0x4e 2a:* 48 8b 4a 08 mov 0x8(%rdx),%rcx <-- trapping instruction 2e: f6 c1 01 test $0x1,%cl 31: 0f 85 cb 00 00 00 jne 0x102 37: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1) 3c: 31 c9 xor %ecx,%ecx 3e: 48 rex.W 3f: f7 .byte 0xf7
Code starting with the faulting instruction
0: 48 8b 4a 08 mov 0x8(%rdx),%rcx 4: f6 c1 01 test $0x1,%cl 7: 0f 85 cb 00 00 00 jne 0xd8 d: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1) 12: 31 c9 xor %ecx,%ecx 14: 48 rex.W 15: f7 .byte 0xf7[ 991.201691] RSP: 0018:ffffb11281d0ba90 EFLAGS: 00010202 [ 991.206910] RAX: ffffe14ec4208000 RBX: 0000000000005000 RCX: 0000000000000009 [ 991.214033] RDX: 0000000000000000 RSI: 0000000000000006 RDI: 0000000000001000 [ 991.221156] RBP: ffffb11281d0bb88 R08: 00000000000020ff R09: ffffe14ec4208000 [ 991.228280] R10: 0000000000000005 R11: 0000000000000006 R12: ffff96b4825f4200 [ 991.235406] R13: 0000000000000001 R14: 000000003d6277bf R15: 0000000000000000 [ 991.242529] FS: 00007f41e80b9740(0000) GS:ffff96b83bc1b000(0000) knlGS:0000000000000000 [ 991.250608] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 991.256378] CR2: 0000000000000008 CR3: 0000000106c42003 CR4: 00000000003706f0 [ 991.263513] Call Trace: [ 991.265956] <TASK> [ 991.268055] __zerocopy_sg_from_iter (net/core/datagram.c:?) [ 991.272674] ? kmalloc_reserve (net/core/skbuff.c:581) [ 991.276599] skb_zerocopy_iter_stream (net/core/skbuff.c:1867) [ 991.281219] tcp_sendmsg_locked (net/ipv4/tcp.c:1283) [ 991.285493] tcp_sendmsg (net/ipv4/tcp.c:1393) [ 991.288896] inet6_sendmsg (net/ipv6/af_inet6.c:661) [ 991.292466] __sock_sendmsg (net/socket.c:717) [ 991.296126] __sys_sendto (net/socket.c:?) [ 991.299785] __x64_sys_sendto (net/socket.c:2235 net/socket.c:2231 net/socket.c:2231) [ 991.303622] x64_sys_call (arch/x86/entry/syscall_64.c:41) [ 991.307462] do_syscall_64 (arch/x86/entry/syscall_64.c:?) [ 991.311128] ? irqentry_exit (kernel/entry/common.c:210) [ 991.314881] ? exc_page_fault (arch/x86/mm/fault.c:1536) [ 991.318720] entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) [ 991.323762] RIP: 0033:0x7f41e814b687 [ 991.327352] Code: 48 89 fa 4c 89 df e8 58 b3 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff All code ======== 0: 48 89 fa mov %rdi,%rdx 3: 4c 89 df mov %r11,%rdi 6: e8 58 b3 00 00 call 0xb363 b: 8b 93 08 03 00 00 mov 0x308(%rbx),%edx 11: 59 pop %rcx 12: 5e pop %rsi 13: 48 83 f8 fc cmp $0xfffffffffffffffc,%rax 17: 74 1a je 0x33 19: 5b pop %rbx 1a: c3 ret 1b: 0f 1f 84 00 00 00 00 nopl 0x0(%rax,%rax,1) 22: 00 23: 48 8b 44 24 10 mov 0x10(%rsp),%rax 28: 0f 05 syscall 2a:* 5b pop %rbx <-- trapping instruction 2b: c3 ret 2c: 0f 1f 80 00 00 00 00 nopl 0x0(%rax) 33: 83 e2 39 and $0x39,%edx 36: 83 fa 08 cmp $0x8,%edx 39: 75 de jne 0x19 3b: e8 23 ff ff ff call 0xffffffffffffff63
Code starting with the faulting instruction
0: 5b pop %rbx 1: c3 ret 2: 0f 1f 80 00 00 00 00 nopl 0x0(%rax) 9: 83 e2 39 and $0x39,%edx c: 83 fa 08 cmp $0x8,%edx f: 75 de jne 0xffffffffffffffef 11: e8 23 ff ff ff call 0xffffffffffffff39[ 991.346124] RSP: 002b:00007ffdd843ba50 EFLAGS: 00000202 ORIG_RAX: 000000000000002c [ 991.353680] RAX: ffffffffffffffda RBX: 00007f41e80b9740 RCX: 00007f41e814b687 [ 991.360806] RDX: 000000000000f180 RSI: 000056251f1fd100 RDI: 0000000000000005 [ 991.367931] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 [ 991.375063] R10: 0000000004000000 R11: 0000000000000202 R12: 0000000000000000 [ 991.382193] R13: 000056251f1fb080 R14: 000001a670e438d8 R15: 0000000000000005 [ 991.389357] </TASK> [ 991.391571] Modules linked in: mptcp_diag tcp_diag inet_diag xt_conntrack xfrm_user ipip bridge stp llc geneve vxlan act_csum act_pedit openvswitch nsh nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 psample cls_flower sch_prio xt_mark nft_compat nf_tables sch_ingress act_mirred cls_basic sch_fq_codel vrf pktgen macvtap macvlan tap x86_pkg_temp_thermal ip_tables x_tables [last unloaded: test_bpf] [ 991.426812] CR2: 0000000000000008 [ 991.430121] ---[ end trace 0000000000000000 ]--- [ 991.434733] RIP: 0010:zerocopy_fill_skb_from_iter (include/linux/page-flags.h:284) [ 991.440477] Code: 4d 85 c0 0f 84 04 01 00 00 44 39 c7 41 0f 4d f8 4c 63 de 4a 8b 54 dc 30 49 89 d6 4d 29 ce 49 c1 fe 06 49 d3 ee 4d 85 f6 74 24 <48> 8b 4a 08 f6 c1 01 0f 85 cb 00 00 00 0f 1f 44 00 00 31 c9 48 f7 All code ======== 0: 4d 85 c0 test %r8,%r8 3: 0f 84 04 01 00 00 je 0x10d 9: 44 39 c7 cmp %r8d,%edi c: 41 0f 4d f8 cmovge %r8d,%edi 10: 4c 63 de movslq %esi,%r11 13: 4a 8b 54 dc 30 mov 0x30(%rsp,%r11,8),%rdx 18: 49 89 d6 mov %rdx,%r14 1b: 4d 29 ce sub %r9,%r14 1e: 49 c1 fe 06 sar $0x6,%r14 22: 49 d3 ee shr %cl,%r14 25: 4d 85 f6 test %r14,%r14 28: 74 24 je 0x4e 2a:* 48 8b 4a 08 mov 0x8(%rdx),%rcx <-- trapping instruction 2e: f6 c1 01 test $0x1,%cl 31: 0f 85 cb 00 00 00 jne 0x102 37: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1) 3c: 31 c9 xor %ecx,%ecx 3e: 48 rex.W 3f: f7 .byte 0xf7
Code starting with the faulting instruction
0: 48 8b 4a 08 mov 0x8(%rdx),%rcx 4: f6 c1 01 test $0x1,%cl 7: 0f 85 cb 00 00 00 jne 0xd8 d: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1) 12: 31 c9 xor %ecx,%ecx 14: 48 rex.W 15: f7 .byte 0xf7[ 991.459215] RSP: 0018:ffffb11281d0ba90 EFLAGS: 00010202 [ 991.464434] RAX: ffffe14ec4208000 RBX: 0000000000005000 RCX: 0000000000000009 [ 991.471557] RDX: 0000000000000000 RSI: 0000000000000006 RDI: 0000000000001000 [ 991.478681] RBP: ffffb11281d0bb88 R08: 00000000000020ff R09: ffffe14ec4208000 [ 991.485807] R10: 0000000000000005 R11: 0000000000000006 R12: ffff96b4825f4200 [ 991.492930] R13: 0000000000000001 R14: 000000003d6277bf R15: 0000000000000000 [ 991.500054] FS: 00007f41e80b9740(0000) GS:ffff96b83bc1b000(0000) knlGS:0000000000000000 [ 991.508132] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 991.513870] CR2: 0000000000000008 CR3: 0000000106c42003 CR4: 00000000003706f0 [ 991.520994] note: udpgso_bench_tx[64842] exited with irqs disabled
## Source
- Kernel version: 6.17.0-rc4
- Git tree: https://kernel.googlesource.com/pub/scm/linux/kernel/git/next/linux-next.git
- Git describe: next-20250905
- Git commit: be5d4872e528796df9d7425f2bd9b3893eb3a42c
- Architectures: x86_64
- Toolchains: clang-nightly
- Kconfigs: defconfig+selftests/*/config
## Build
- Test log: https://qa-reports.linaro.org/api/testruns/29777495/log_file/
- LAVA test log: https://lkft.validation.linaro.org/scheduler/job/8434053#L16943
- Test details:
https://regressions.linaro.org/lkft/linux-next-master/next-20250905/log-pars...
- Test plan: https://tuxapi.tuxsuite.com/v1/groups/linaro/projects/lkft/tests/32GkXBGNRND...
- Build link: https://storage.tuxsuite.com/public/linaro/lkft/builds/32GkU7mdlpISpPeeeEwIf...
- Kernel config:
https://storage.tuxsuite.com/public/linaro/lkft/builds/32GkU7mdlpISpPeeeEwIf...
-- Linaro LKFT https://lkft.linaro.org
I suspect a bug added in mm/gup.c recently
commit db076b5db550aa34169dceee81d0974c7b2a2482 Author: David Hildenbrand david@redhat.com Date: Mon Sep 1 17:03:40 2025 +0200
mm/gup: remove record_subpages() We can just cleanup the code by calculating the #refs earlier, so we can just inline what remains of record_subpages(). Calculate the number of references/pages ahead of times, and record them only once all our tests passed. Link: https://lkml.kernel.org/r/20250901150359.867252-20-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>Yes, fix already on its way:
https://lkml.kernel.org/r/5090355d-546a-4d06-99e1-064354d156b5@redhat.com
#syz dup: [syzbot] [io-uring?] KASAN: null-ptr-deref Read in io_sqe_buffer_register
Sorry for the noise, realized just now that this was not a syzkaller report. :)