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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 05.09.25 01:20, Jens Axboe wrote: > On 9/4/25 9:36 AM, syzbot wrote: >> Hello, >> >> syzbot found the following issue on: >> >> HEAD commit: 4ac65880ebca Add linux-next specific files for 20250904 >> git tree: linux-next >> console output: https://syzkaller.appspot.com/x/log.txt?x=1785fe62580000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=fbc16d9faf3a88a4 >> dashboard link: https://syzkaller.appspot.com/bug?extid=1ab243d3eebb2aabf4a4 >> compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8 >> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13f23e62580000 >> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12cb6312580000 >> >> Downloadable assets: >> disk image: https://storage.googleapis.com/syzbot-assets/36645a51612c/disk-4ac65880.raw.xz >> vmlinux: https://storage.googleapis.com/syzbot-assets/bba80d634bef/vmlinux-4ac65880.xz >> kernel image: https://storage.googleapis.com/syzbot-assets/e58dd70dfd0f/bzImage-4ac65880.xz >> >> IMPORTANT: if you fix the issue, please add the following tag to the commit: >> Reported-by: syzbot+1ab243d3eebb2aabf4a4@syzkaller.appspotmail.com >> >> ================================================================== >> BUG: KASAN: null-ptr-deref in instrument_atomic_read include/linux/instrumented.h:68 [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 PageCompound include/linux/page-flags.h:331 [inline] >> BUG: KASAN: null-ptr-deref in io_buffer_account_pin io_uring/rsrc.c:668 [inline] >> BUG: KASAN: null-ptr-deref in io_sqe_buffer_register+0x369/0x20a0 io_uring/rsrc.c:817 >> Read of size 8 at addr 0000000000000000 by task syz.0.17/6020 >> >> CPU: 0 UID: 0 PID: 6020 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) >> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025 >> Call Trace: >> >> dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120 >> kasan_report+0x118/0x150 mm/kasan/report.c:595 >> check_region_inline mm/kasan/generic.c:-1 [inline] >> kasan_check_range+0x2b0/0x2c0 mm/kasan/generic.c:200 >> instrument_atomic_read include/linux/instrumented.h:68 [inline] >> _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline] >> PageCompound include/linux/page-flags.h:331 [inline] >> io_buffer_account_pin io_uring/rsrc.c:668 [inline] >> io_sqe_buffer_register+0x369/0x20a0 io_uring/rsrc.c:817 >> __io_sqe_buffers_update io_uring/rsrc.c:322 [inline] >> __io_register_rsrc_update+0x55e/0x11b0 io_uring/rsrc.c:360 >> io_register_rsrc_update+0x196/0x1a0 io_uring/rsrc.c:391 >> __io_uring_register io_uring/register.c:736 [inline] >> __do_sys_io_uring_register io_uring/register.c:926 [inline] >> __se_sys_io_uring_register+0x795/0x11b0 io_uring/register.c:903 >> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] >> do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94 >> entry_SYSCALL_64_after_hwframe+0x77/0x7f >> RIP: 0033:0x7f99b1f8ebe9 >> Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48 >> RSP: 002b:00007f99b2d88038 EFLAGS: 00000246 ORIG_RAX: 00000000000001ab >> RAX: ffffffffffffffda RBX: 00007f99b21c5fa0 RCX: 00007f99b1f8ebe9 >> RDX: 00002000000003c0 RSI: 0000000000000010 RDI: 0000000000000003 >> RBP: 00007f99b2011e19 R08: 0000000000000000 R09: 0000000000000000 >> R10: 0000000000000020 R11: 0000000000000246 R12: 0000000000000000 >> R13: 00007f99b21c6038 R14: 00007f99b21c5fa0 R15: 00007ffeadfa5958 >> >> ================================================================== #syz test From bfd07c995814354f6b66c5b6a72e96a7aa9fb73b Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Fri, 5 Sep 2025 08:38:43 +0200 Subject: [PATCH] fixup: mm/gup: remove record_subpages() pages is not adjusted by the caller, but idnexed by existing *nr. Signed-off-by: David Hildenbrand --- mm/gup.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/gup.c b/mm/gup.c index 010fe56f6e132..22420f2069ee1 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -2981,6 +2981,7 @@ static int gup_fast_pmd_leaf(pmd_t orig, pmd_t *pmdp, unsigned long addr, return 0; } + pages += *nr; *nr += refs; for (; refs; refs--) *(pages++) = page++; @@ -3024,6 +3025,7 @@ static int gup_fast_pud_leaf(pud_t orig, pud_t *pudp, unsigned long addr, return 0; } + pages += *nr; *nr += refs; for (; refs; refs--) *(pages++) = page++; -- 2.50.1 -- Cheers David / dhildenb