> On 14 Feb 2025, at 10:48, syzbot wrote: > >> Hello, >> >> syzbot found the following issue on: >> >> HEAD commit: df5d6180169a Add linux-next specific files for 20250210 >> git tree: linux-next >> console+strace: https://syzkaller.appspot.com/x/log.txt?x=16d343f8580000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=2cd616b6e736ca7 >> dashboard link: https://syzkaller.appspot.com/bug?extid=012c6245eaea0e23f7f9 >> compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 >> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=138972a4580000 >> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11737b18580000 >> >> Downloadable assets: >> disk image: https://storage.googleapis.com/syzbot-assets/92495cf20271/disk-df5d6180.raw.xz >> vmlinux: https://storage.googleapis.com/syzbot-assets/4b3656161842/vmlinux-df5d6180.xz >> kernel image: https://storage.googleapis.com/syzbot-assets/7fbc4e7a0f5d/bzImage-df5d6180.xz >> >> The issue was bisected to: >> >> commit 19c067c8a0f18b62d4a4235b0b327624c86f2e40 >> Author: Zi Yan <ziy@xxxxxxxxxx> >> Date: Wed Feb 5 03:14:13 2025 +0000 >> >> mm/huge_memory: add buddy allocator like folio_split() >> >> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=102f9bdf980000 >> final oops: https://syzkaller.appspot.com/x/report.txt?x=122f9bdf980000 >> console output: https://syzkaller.appspot.com/x/log.txt?x=142f9bdf980000 >> >> IMPORTANT: if you fix the issue, please add the following tag to the commit: >> Reported-by: syzbot+012c6245eaea0e23f7f9@xxxxxxxxxxxxxxxxxxxxxxxxx >> Fixes: 19c067c8a0f1 ("mm/huge_memory: add buddy allocator like folio_split()") >> >> Oops: general protection fault, probably for non-canonical address 0xdffffc0000000024: 0000 [#1] PREEMPT SMP KASAN PTI >> KASAN: null-ptr-deref in range [0x0000000000000120-0x0000000000000127] >> CPU: 1 UID: 0 PID: 5949 Comm: syz-executor163 Not tainted 6.14.0-rc2-next-20250210-syzkaller #0 >> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024 >> RIP: 0010:shmem_mapping+0x25/0x50 mm/shmem.c:281 >> Code: 90 90 90 90 90 f3 0f 1e fa 53 48 89 fb e8 c3 3a bd ff 48 81 c3 20 01 00 00 48 89 d8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df <80> 3c 08 00 74 08 48 89 df e8 dd 35 24 00 48 c7 c0 80 6c 14 8c 48 >> RSP: 0018:ffffc90004036dd8 EFLAGS: 00010006 >> RAX: 0000000000000024 RBX: 0000000000000120 RCX: dffffc0000000000 >> RDX: 0000000000000000 RSI: 0000000000000600 RDI: 0000000000000000 >> RBP: 0000000000000600 R08: ffffffff822bcf18 R09: 1ffffd4000331008 >> R10: dffffc0000000000 R11: fffff94000331009 R12: ffffea0001988018 >> R13: ffffea0001988080 R14: ffffea0001988018 R15: ffffea0001988000 >> FS: 00007f5e045316c0(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000 >> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> CR2: 00007f5e0458dae0 CR3: 0000000023c78000 CR4: 00000000003526f0 >> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 >> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 >> Call Trace: >> <TASK> >> __split_unmapped_folio+0x238a/0x3e50 mm/huge_memory.c:3587 >> __folio_split+0x1267/0x16d0 mm/huge_memory.c:3871 >> try_folio_split include/linux/huge_mm.h:374 [inline] >> truncate_inode_partial_folio+0x55d/0xdc0 mm/truncate.c:230 >> shmem_undo_range+0xab7/0x1820 mm/shmem.c:1144 >> shmem_truncate_range mm/shmem.c:1224 [inline] >> shmem_fallocate+0x431/0xf20 mm/shmem.c:3674 >> vfs_fallocate+0x623/0x7a0 fs/open.c:338 >> madvise_remove mm/madvise.c:1034 [inline] >> madvise_vma_behavior mm/madvise.c:1269 [inline] >> madvise_walk_vmas mm/madvise.c:1511 [inline] >> madvise_do_behavior+0x1f29/0x3c00 mm/madvise.c:1646 >> do_madvise mm/madvise.c:1744 [inline] >> __do_sys_madvise mm/madvise.c:1752 [inline] >> __se_sys_madvise mm/madvise.c:1750 [inline] >> __x64_sys_madvise+0x11b/0x140 mm/madvise.c:1750 >> do_syscall_x64 arch/x86/entry/common.c:52 [inline] >> do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 >> entry_SYSCALL_64_after_hwframe+0x77/0x7f >> RIP: 0033:0x7f5e04576519 >> Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 51 18 00 00 90 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 b0 ff ff ff f7 d8 64 89 01 48 >> RSP: 002b:00007f5e04531218 EFLAGS: 00000246 ORIG_RAX: 000000000000001c >> RAX: ffffffffffffffda RBX: 00007f5e04600308 RCX: 00007f5e04576519 >> RDX: 0000000000000009 RSI: 0000000000600003 RDI: 0000400000000000 >> RBP: 00007f5e04600300 R08: 0000000000000000 R09: 0000000000000000 >> R10: 0000000000000000 R11: 0000000000000246 R12: 00007f5e045cd074 >> R13: 0000400000000000 R14: 0000400000000140 R15: 0000400000000040 >> </TASK> >> Modules linked in: >> ---[ end trace 0000000000000000 ]--- >> RIP: 0010:shmem_mapping+0x25/0x50 mm/shmem.c:281 >> Code: 90 90 90 90 90 f3 0f 1e fa 53 48 89 fb e8 c3 3a bd ff 48 81 c3 20 01 00 00 48 89 d8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df <80> 3c 08 00 74 08 48 89 df e8 dd 35 24 00 48 c7 c0 80 6c 14 8c 48 >> RSP: 0018:ffffc90004036dd8 EFLAGS: 00010006 >> RAX: 0000000000000024 RBX: 0000000000000120 RCX: dffffc0000000000 >> RDX: 0000000000000000 RSI: 0000000000000600 RDI: 0000000000000000 >> RBP: 0000000000000600 R08: ffffffff822bcf18 R09: 1ffffd4000331008 >> R10: dffffc0000000000 R11: fffff94000331009 R12: ffffea0001988018 >> R13: ffffea0001988080 R14: ffffea0001988018 R15: ffffea0001988000 >> FS: 00007f5e045316c0(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000 >> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> CR2: 00007f5e0458dae0 CR3: 0000000023c78000 CR4: 00000000003526f0 >> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 >> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 >> ---------------- >> Code disassembly (best guess): >> 0: 90 nop >> 1: 90 nop >> 2: 90 nop >> 3: 90 nop >> 4: 90 nop >> 5: f3 0f 1e fa endbr64 >> 9: 53 push %rbx >> a: 48 89 fb mov %rdi,%rbx >> d: e8 c3 3a bd ff call 0xffbd3ad5 >> 12: 48 81 c3 20 01 00 00 add $0x120,%rbx >> 19: 48 89 d8 mov %rbx,%rax >> 1c: 48 c1 e8 03 shr $0x3,%rax >> 20: 48 b9 00 00 00 00 00 movabs $0xdffffc0000000000,%rcx >> 27: fc ff df >> * 2a: 80 3c 08 00 cmpb $0x0,(%rax,%rcx,1) <-- trapping instruction >> 2e: 74 08 je 0x38 >> 30: 48 89 df mov %rbx,%rdi >> 33: e8 dd 35 24 00 call 0x243615 >> 38: 48 c7 c0 80 6c 14 8c mov $0xffffffff8c146c80,%rax >> 3f: 48 rex.W >> > > > #syz test: github.com:x-y-z/linux-1gb-thp.git syzkaller_fix_20250114 "github.com:x-y-z/linux-1gb-thp.git" does not look like a valid git repo address. > > origin_folio->mapping becomes NULL, since it was dropped, and the remaining > after-split folios are still trying to use origin_folio->mapping. It leads > to the error. And the original __split_huge_page() did not check > origin_folio->index nor dropped it. __split_unmapped_folio() should keep > the original behavior. > > Fixed it by not dropping origin_folio. > > My local test do not fail and I am triggering syzbot to test the change > to confirm it. > > Best Regards, > Yan, Zi
