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id 006d021491bc7-67e0967a47emr1961033eaf.0.1774544341438; Thu, 26 Mar 2026 09:59:01 -0700 (PDT) Date: Thu, 26 Mar 2026 09:59:01 -0700 In-Reply-To: <20260326145044.29484-1-kartikey406@gmail.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <69c565d5.050a0220.330c49.0007.GAE@google.com> Subject: Re: [syzbot] [ext4?] KASAN: use-after-free Read in xattr_find_entry (2) From: syzbot To: kartikey406@gmail.com, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot has tested the proposed patch but the reproducer is still triggering an issue: KASAN: use-after-free Read in xattr_find_entry loop0: detected capacity change from 1024 to 64 ================================================================== BUG: KASAN: use-after-free in xattr_find_entry+0x1a5/0x280 fs/ext4/xattr.c:334 Read of size 4 at addr ffff88806233f004 by task syz.0.17/6393 CPU: 1 UID: 49663 PID: 6393 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0xba/0x230 mm/kasan/report.c:482 kasan_report+0x117/0x150 mm/kasan/report.c:595 xattr_find_entry+0x1a5/0x280 fs/ext4/xattr.c:334 ext4_xattr_ibody_get+0x232/0x4c0 fs/ext4/xattr.c:655 ext4_xattr_get+0x123/0x6a0 fs/ext4/xattr.c:709 ext4_get_acl+0x84/0x930 fs/ext4/acl.c:165 __get_acl+0x27e/0x410 fs/posix_acl.c:159 check_acl+0x3a/0x150 fs/namei.c:385 acl_permission_check fs/namei.c:471 [inline] generic_permission+0x497/0x690 fs/namei.c:524 do_inode_permission fs/namei.c:585 [inline] inode_permission+0x243/0x5f0 fs/namei.c:648 lookup_inode_permission_may_exec fs/namei.c:-1 [inline] may_lookup fs/namei.c:1973 [inline] link_path_walk+0x1149/0x18d0 fs/namei.c:2595 path_lookupat+0xe4/0x8c0 fs/namei.c:2803 filename_lookup+0x256/0x5d0 fs/namei.c:2833 user_path_at+0x40/0x160 fs/namei.c:3612 do_mount fs/namespace.c:4169 [inline] __do_sys_mount fs/namespace.c:4361 [inline] __se_sys_mount+0x2dc/0x420 fs/namespace.c:4338 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f14f759c629 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:00007f14f845c028 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5 RAX: ffffffffffffffda RBX: 00007f14f7815fa0 RCX: 00007f14f759c629 RDX: 0000000000000000 RSI: 0000200000000040 RDI: 0000000000000000 RBP: 00007f14f7632b39 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000002094080 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f14f7816038 R14: 00007f14f7815fa0 R15: 00007ffd4455cb58 The buggy address belongs to the physical page: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x3c9 pfn:0x6233f flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff) raw: 00fff00000000000 ffffea000188d008 ffffea0001cecd88 0000000000000000 raw: 00000000000003c9 0000000000000000 00000000ffffffff 0000000000000000 page dumped because: kasan: bad access detected page_owner tracks the page as freed page last allocated via order 0, migratetype Movable, gfp_mask 0x140cca(GFP_HIGHUSER_MOVABLE|__GFP_COMP), pid 6183, tgid 6183 (syz-executor), ts 130974047320, free_ts 131341169720 set_page_owner include/linux/page_owner.h:32 [inline] post_alloc_hook+0x231/0x280 mm/page_alloc.c:1889 prep_new_page mm/page_alloc.c:1897 [inline] get_page_from_freelist+0x24dc/0x2580 mm/page_alloc.c:3962 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5250 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2484 folio_alloc_mpol_noprof mm/mempolicy.c:2503 [inline] vma_alloc_folio_noprof+0xea/0x210 mm/mempolicy.c:2538 folio_prealloc mm/memory.c:-1 [inline] do_cow_fault mm/memory.c:5823 [inline] do_fault mm/memory.c:5935 [inline] do_pte_missing+0x4ea/0x3490 mm/memory.c:4477 handle_pte_fault mm/memory.c:6317 [inline] __handle_mm_fault mm/memory.c:6455 [inline] handle_mm_fault+0x1bec/0x3310 mm/memory.c:6624 do_user_addr_fault+0xa73/0x1340 arch/x86/mm/fault.c:1334 handle_page_fault arch/x86/mm/fault.c:1474 [inline] exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1527 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618 page last free pid 6184 tgid 6184 stack trace: reset_page_owner include/linux/page_owner.h:25 [inline] __free_pages_prepare mm/page_alloc.c:1433 [inline] free_unref_folios+0xed5/0x16d0 mm/page_alloc.c:3040 folios_put_refs+0x789/0x8d0 mm/swap.c:1002 free_pages_and_swap_cache+0x2e7/0x5b0 mm/swap_state.c:423 __tlb_batch_free_encoded_pages mm/mmu_gather.c:138 [inline] tlb_batch_pages_flush mm/mmu_gather.c:151 [inline] tlb_flush_mmu_free mm/mmu_gather.c:398 [inline] tlb_flush_mmu+0x6d3/0xa30 mm/mmu_gather.c:405 tlb_finish_mmu+0xf9/0x230 mm/mmu_gather.c:530 exit_mmap+0x498/0xa10 mm/mmap.c:1315 __mmput+0x118/0x430 kernel/fork.c:1175 exit_mm+0x168/0x220 kernel/exit.c:581 do_exit+0x6a2/0x23c0 kernel/exit.c:964 do_group_exit+0x21b/0x2d0 kernel/exit.c:1118 get_signal+0x1284/0x1330 kernel/signal.c:3034 arch_do_signal_or_restart+0xbc/0x830 arch/x86/kernel/signal.c:337 __exit_to_user_mode_loop kernel/entry/common.c:64 [inline] exit_to_user_mode_loop+0x86/0x480 kernel/entry/common.c:98 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline] syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline] syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline] do_syscall_64+0x32d/0xf80 arch/x86/entry/syscall_64.c:100 entry_SYSCALL_64_after_hwframe+0x77/0x7f Memory state around the buggy address: ffff88806233ef00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff88806233ef80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >ffff88806233f000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ^ ffff88806233f080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ffff88806233f100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ================================================================== Tested on: commit: 0138af24 Merge tag 'erofs-for-7.0-rc6-fixes' of git://.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=13bad06a580000 kernel config: https://syzkaller.appspot.com/x/.config?x=b643133b3e44c9fd dashboard link: https://syzkaller.appspot.com/bug?extid=fb32afec111a7d61b939 compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8 patch: https://syzkaller.appspot.com/x/patch.diff?x=16da8eda580000