syzbot has found a reproducer for the following issue on: HEAD commit: 3f667b5d4053 Merge tag 'tty-5.16-rc6' of git://git.kernel... git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=174324a3b00000 kernel config: https://syzkaller.appspot.com/x/.config?x=fa556098924b78f0 dashboard link: https://syzkaller.appspot.com/bug?extid=2c56b725ec547fa9cb29 compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14df5c71b00000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11d67495b00000 The issue was bisected to: commit 284562e1f34874e267d4f499362c3816f8f6bc3f Author: Gurchetan Singh <gurchetansingh@xxxxxxxxxxxx> Date: Tue Dec 3 01:36:27 2019 +0000 udmabuf: implement begin_cpu_access/end_cpu_access hooks bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=12d68447300000 final oops: https://syzkaller.appspot.com/x/report.txt?x=11d68447300000 console output: https://syzkaller.appspot.com/x/log.txt?x=16d68447300000 IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+2c56b725ec547fa9cb29@xxxxxxxxxxxxxxxxxxxxxxxxx Fixes: 284562e1f348 ("udmabuf: implement begin_cpu_access/end_cpu_access hooks") general protection fault, probably for non-canonical address 0xdffffc0000000002: 0000 [#1] PREEMPT SMP KASAN KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017] CPU: 1 PID: 3595 Comm: syz-executor559 Not tainted 5.16.0-rc5-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:sg_alloc_append_table_from_pages+0x821/0xdb0 lib/scatterlist.c:525 lib/scatterlist.c:525 Code: 0c 24 48 8b 4c 24 48 48 39 c8 48 0f 46 c8 89 f0 4c 8d 3c c7 48 89 4c 24 30 48 b9 00 00 00 00 00 fc ff df 4c 89 f8 48 c1 e8 03 <80> 3c 08 00 0f 85 24 05 00 00 4d 8b 3f 4c 89 e0 31 ff 83 e0 03 48 RSP: 0018:ffffc90002d0fc48 EFLAGS: 00010212 RAX: 0000000000000002 RBX: 0000000000000001 RCX: dffffc0000000000 RDX: ffff888021fd5700 RSI: 0000000000000000 RDI: 0000000000000010 RBP: 00000000fffff000 R08: fffffffffffff000 R09: ffff8880189ddb00 R10: ffffffff83d88b30 R11: 0000000000000000 R12: 0000000000000002 R13: ffff8880189ddb00 R14: 0000000000000000 R15: 0000000000000010 FS: 000055555652c300(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000020005b4c CR3: 00000000176ae000 CR4: 0000000000350ee0 Call Trace: <TASK> sg_alloc_table_from_pages_segment+0xc9/0x260 lib/scatterlist.c:573 lib/scatterlist.c:573 sg_alloc_table_from_pages include/linux/scatterlist.h:331 [inline] sg_alloc_table_from_pages include/linux/scatterlist.h:331 [inline] drivers/dma-buf/udmabuf.c:67 get_sg_table.isra.0+0xbb/0x160 drivers/dma-buf/udmabuf.c:67 drivers/dma-buf/udmabuf.c:67 begin_cpu_udmabuf+0x130/0x1d0 drivers/dma-buf/udmabuf.c:126 drivers/dma-buf/udmabuf.c:126 dma_buf_begin_cpu_access+0xfd/0x1d0 drivers/dma-buf/dma-buf.c:1175 drivers/dma-buf/dma-buf.c:1175 dma_buf_ioctl+0x29a/0x380 drivers/dma-buf/dma-buf.c:374 drivers/dma-buf/dma-buf.c:374 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl fs/ioctl.c:860 [inline] vfs_ioctl fs/ioctl.c:51 [inline] fs/ioctl.c:860 __do_sys_ioctl fs/ioctl.c:874 [inline] fs/ioctl.c:860 __se_sys_ioctl fs/ioctl.c:860 [inline] fs/ioctl.c:860 __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860 fs/ioctl.c:860 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_x64 arch/x86/entry/common.c:50 [inline] arch/x86/entry/common.c:80 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7f57966b60a9 Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 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 c0 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffea34a0a78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f57966b60a9 RDX: 0000000020000000 RSI: 0000000040086200 RDI: 0000000000000004 RBP: 00007f579667a090 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f579667a120 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 </TASK> Modules linked in: ---[ end trace ed55bd5e5ccee2ad ]--- RIP: 0010:sg_alloc_append_table_from_pages+0x821/0xdb0 lib/scatterlist.c:525 lib/scatterlist.c:525 Code: 0c 24 48 8b 4c 24 48 48 39 c8 48 0f 46 c8 89 f0 4c 8d 3c c7 48 89 4c 24 30 48 b9 00 00 00 00 00 fc ff df 4c 89 f8 48 c1 e8 03 <80> 3c 08 00 0f 85 24 05 00 00 4d 8b 3f 4c 89 e0 31 ff 83 e0 03 48 RSP: 0018:ffffc90002d0fc48 EFLAGS: 00010212 RAX: 0000000000000002 RBX: 0000000000000001 RCX: dffffc0000000000 RDX: ffff888021fd5700 RSI: 0000000000000000 RDI: 0000000000000010 RBP: 00000000fffff000 R08: fffffffffffff000 R09: ffff8880189ddb00 R10: ffffffff83d88b30 R11: 0000000000000000 R12: 0000000000000002 R13: ffff8880189ddb00 R14: 0000000000000000 R15: 0000000000000010 FS: 000055555652c300(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000055c8ef357220 CR3: 00000000176ae000 CR4: 0000000000350ef0 ---------------- Code disassembly (best guess): 0: 0c 24 or $0x24,%al 2: 48 8b 4c 24 48 mov 0x48(%rsp),%rcx 7: 48 39 c8 cmp %rcx,%rax a: 48 0f 46 c8 cmovbe %rax,%rcx e: 89 f0 mov %esi,%eax 10: 4c 8d 3c c7 lea (%rdi,%rax,8),%r15 14: 48 89 4c 24 30 mov %rcx,0x30(%rsp) 19: 48 b9 00 00 00 00 00 movabs $0xdffffc0000000000,%rcx 20: fc ff df 23: 4c 89 f8 mov %r15,%rax 26: 48 c1 e8 03 shr $0x3,%rax * 2a: 80 3c 08 00 cmpb $0x0,(%rax,%rcx,1) <-- trapping instruction 2e: 0f 85 24 05 00 00 jne 0x558 34: 4d 8b 3f mov (%r15),%r15 37: 4c 89 e0 mov %r12,%rax 3a: 31 ff xor %edi,%edi 3c: 83 e0 03 and $0x3,%eax 3f: 48 rex.W ---------------- Code disassembly (best guess): 0: 0c 24 or $0x24,%al 2: 48 8b 4c 24 48 mov 0x48(%rsp),%rcx 7: 48 39 c8 cmp %rcx,%rax a: 48 0f 46 c8 cmovbe %rax,%rcx e: 89 f0 mov %esi,%eax 10: 4c 8d 3c c7 lea (%rdi,%rax,8),%r15 14: 48 89 4c 24 30 mov %rcx,0x30(%rsp) 19: 48 b9 00 00 00 00 00 movabs $0xdffffc0000000000,%rcx 20: fc ff df 23: 4c 89 f8 mov %r15,%rax 26: 48 c1 e8 03 shr $0x3,%rax * 2a: 80 3c 08 00 cmpb $0x0,(%rax,%rcx,1) <-- trapping instruction 2e: 0f 85 24 05 00 00 jne 0x558 34: 4d 8b 3f mov (%r15),%r15 37: 4c 89 e0 mov %r12,%rax 3a: 31 ff xor %edi,%edi 3c: 83 e0 03 and $0x3,%eax 3f: 48 rex.W
