Subject: [syzbot] [bpf?] [net?] KASAN: stack-out-of-bounds Read in xdp_do_check_flushed

From: syzbot <[email-masked]>
Date: Fri, 12 Jul 2024 09:25:24 -0700

Hello,

syzbot found the following issue on:

HEAD commit:    523b23f0bee3 Add linux-next specific files for 20240710
git tree:       linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=13187c7e980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=98dd8c4bab5cdce
dashboard link: https://syzkaller.appspot.com/bug?extid=709e4c85c904bcd62735
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=106dd859980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=111637b9980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/345bcd25ed2f/disk-523b23f0.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a4508962d345/vmlinux-523b23f0.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4ba5eb555639/bzImage-523b23f0.xz

The issue was bisected to:

commit fecef4cd42c689a200bdd39e6fffa71475904bc1
Author: Sebastian Andrzej Siewior <[email-masked]>
Date:   Thu Jul 4 14:48:15 2024 +0000

    tun: Assign missing bpf_net_context.

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=164d6f76980000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=154d6f76980000
console output: https://syzkaller.appspot.com/x/log.txt?x=114d6f76980000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]
Fixes: fecef4cd42c6 ("tun: Assign missing bpf_net_context.")

==================================================================
BUG: KASAN: stack-out-of-bounds in bpf_net_ctx_get_all_used_flush_lists include/linux/filter.h:837 [inline]
BUG: KASAN: stack-out-of-bounds in xdp_do_check_flushed+0x231/0x240 net/core/filter.c:4298
Read of size 4 at addr ffffc90003def7f8 by task syz-executor156/5107

CPU: 0 UID: 0 PID: 5107 Comm: syz-executor156 Not tainted 6.10.0-rc7-next-20240710-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:377 [inline]
 print_report+0x169/0x550 mm/kasan/report.c:488
 kasan_report+0x143/0x180 mm/kasan/report.c:601
 bpf_net_ctx_get_all_used_flush_lists include/linux/filter.h:837 [inline]
 xdp_do_check_flushed+0x231/0x240 net/core/filter.c:4298
 __napi_poll+0xe4/0x490 net/core/dev.c:6774
 napi_poll net/core/dev.c:6840 [inline]
 net_rx_action+0x89b/0x1240 net/core/dev.c:6962
 handle_softirqs+0x2c4/0x970 kernel/softirq.c:554
 do_softirq+0x11b/0x1e0 kernel/softirq.c:455
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0x1bb/0x200 kernel/softirq.c:382
 local_bh_enable include/linux/bottom_half.h:33 [inline]
 tun_get_user+0x2884/0x4720 drivers/net/tun.c:1936
 tun_chr_write_iter+0x113/0x1f0 drivers/net/tun.c:2052
 new_sync_write fs/read_write.c:497 [inline]
 vfs_write+0xa72/0xc90 fs/read_write.c:590
 ksys_write+0x1a0/0x2c0 fs/read_write.c:643
 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: 0033:0x7f26cdb99d90
Code: 40 00 48 c7 c2 b8 ff ff ff f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 80 3d 11 e3 07 00 00 74 17 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 58 c3 0f 1f 80 00 00 00 00 48 83 ec 28 48 89
RSP: 002b:00007ffd1139eb08 EFLAGS: 00000202 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f26cdb99d90
RDX: 000000000000fdef RSI: 0000000020000200 RDI: 00000000000000c8
RBP: 0000000000000000 R08: 00007ffd1139ec38 R09: 00007ffd1139ec38
R10: 00007ffd1139ec38 R11: 0000000000000202 R12: 0000000000000000
R13: 0000000000000000 R14: 00007ffd1139eb40 R15: 00007ffd1139eb30
 </TASK>

The buggy address belongs to stack of task syz-executor156/5107
 and is located at offset 88 in frame:
 do_softirq+0x0/0x1e0

This frame has 2 objects:
 [32, 40) 'flags.i.i.i105'
 [64, 72) 'flags.i.i.i'

The buggy address belongs to the virtual mapping at
 [ffffc90003de8000, ffffc90003df1000) created by:
 copy_process+0x5d1/0x3d90 kernel/fork.c:2206

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x6b798
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 0000000000000000 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x2dc2(GFP_KERNEL|__GFP_HIGHMEM|__GFP_NOWARN|__GFP_ZERO), pid 5089, tgid 5089 (sshd), ts 45267990588, free_ts 13316620078
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1493
 prep_new_page mm/page_alloc.c:1501 [inline]
 get_page_from_freelist+0x2ccb/0x2d80 mm/page_alloc.c:3480
 __alloc_pages_noprof+0x256/0x6c0 mm/page_alloc.c:4738
 alloc_pages_mpol_noprof+0x3e8/0x680 mm/mempolicy.c:2263
 vm_area_alloc_pages mm/vmalloc.c:3584 [inline]
 __vmalloc_area_node mm/vmalloc.c:3660 [inline]
 __vmalloc_node_range_noprof+0x971/0x1460 mm/vmalloc.c:3841
 alloc_thread_stack_node kernel/fork.c:314 [inline]
 dup_task_struct+0x444/0x8c0 kernel/fork.c:1115
 copy_process+0x5d1/0x3d90 kernel/fork.c:2206
 kernel_clone+0x226/0x8f0 kernel/fork.c:2788
 __do_sys_clone kernel/fork.c:2931 [inline]
 __se_sys_clone kernel/fork.c:2915 [inline]
 __x64_sys_clone+0x258/0x2a0 kernel/fork.c:2915
 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
page last free pid 1 tgid 1 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1094 [inline]
 free_unref_page+0xd22/0xea0 mm/page_alloc.c:2644
 free_contig_range+0x9e/0x160 mm/page_alloc.c:6694
 destroy_args+0x8a/0x890 mm/debug_vm_pgtable.c:1017
 debug_vm_pgtable+0x4be/0x550 mm/debug_vm_pgtable.c:1397
 do_one_initcall+0x248/0x880 init/main.c:1267
 do_initcall_level+0x157/0x210 init/main.c:1329
 do_initcalls+0x3f/0x80 init/main.c:1345
 kernel_init_freeable+0x435/0x5d0 init/main.c:1578
 kernel_init+0x1d/0x2b0 init/main.c:1467
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Memory state around the buggy address:
 ffffc90003def680: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffc90003def700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffffc90003def780: 00 00 00 00 f1 f1 f1 f1 00 f2 f2 f2 00 f3 f3 f3
                                                                ^
 ffffc90003def800: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffc90003def880: f1 f1 f1 f1 00 f3 f3 f3 00 00 00 00 00 00 00 00
==================================================================

---
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