* [syzbot] [bcachefs?] KASAN: slab-use-after-free Read in bch2_reconstruct_alloc
@ 2024-10-23 14:27 syzbot
2024-10-25 10:02 ` Lizhi Xu
0 siblings, 1 reply; 7+ messages in thread
From: syzbot @ 2024-10-23 14:27 UTC (permalink / raw)
To: bfoster, kent.overstreet, linux-bcachefs, linux-kernel,
syzkaller-bugs
Hello,
syzbot found the following issue on:
HEAD commit: 15e7d45e786a Add linux-next specific files for 20241016
git tree: linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=10cbc0a7980000
kernel config: https://syzkaller.appspot.com/x/.config?x=c36416f1c54640c0
dashboard link: https://syzkaller.appspot.com/bug?extid=9fc4dac4775d07bcfe34
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=11c7f487980000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=167b3240580000
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/cf2ad43c81cc/disk-15e7d45e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c85347a66a1c/vmlinux-15e7d45e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/648cf8e59c13/bzImage-15e7d45e.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/bca28bd33502/mount_0.gz
The issue was bisected to:
commit 84f1638795da1ff2084597de4251e9054f1ad728
Author: Kent Overstreet <kent.overstreet@linux.dev>
Date: Fri Dec 29 20:25:07 2023 +0000
bcachefs: bch_sb_field_downgrade
bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=12ca7240580000
final oops: https://syzkaller.appspot.com/x/report.txt?x=11ca7240580000
console output: https://syzkaller.appspot.com/x/log.txt?x=16ca7240580000
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9fc4dac4775d07bcfe34@syzkaller.appspotmail.com
Fixes: 84f1638795da ("bcachefs: bch_sb_field_downgrade")
bcachefs (loop0): recovering from clean shutdown, journal seq 8
bcachefs (loop0): dropping and reconstructing all alloc info
==================================================================
BUG: KASAN: slab-use-after-free in bch2_reconstruct_alloc+0x2af/0xac0 fs/bcachefs/recovery.c:134
Read of size 8 at addr ffff888075728f58 by task syz-executor251/5234
CPU: 1 UID: 0 PID: 5234 Comm: syz-executor251 Not tainted 6.12.0-rc3-next-20241016-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
<TASK>
__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
bch2_reconstruct_alloc+0x2af/0xac0 fs/bcachefs/recovery.c:134
bch2_fs_recovery+0x12dd/0x39a0 fs/bcachefs/recovery.c:842
bch2_fs_start+0x356/0x5b0 fs/bcachefs/super.c:1037
bch2_fs_get_tree+0xd68/0x1710 fs/bcachefs/fs.c:2174
vfs_get_tree+0x90/0x2b0 fs/super.c:1814
do_new_mount+0x2be/0xb40 fs/namespace.c:3507
do_mount fs/namespace.c:3847 [inline]
__do_sys_mount fs/namespace.c:4055 [inline]
__se_sys_mount+0x2d6/0x3c0 fs/namespace.c:4032
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: 0033:0x7fe135241f6a
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 5e 04 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc99fea9d8 EFLAGS: 00000282 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffc99fea9f0 RCX: 00007fe135241f6a
RDX: 0000000020005b00 RSI: 0000000020005b40 RDI: 00007ffc99fea9f0
RBP: 0000000000000004 R08: 00007ffc99feaa30 R09: 0000000000005b27
R10: 0000000000000000 R11: 0000000000000282 R12: 0000000000000000
R13: 00007ffc99feaa30 R14: 0000000000000003 R15: 0000000001000000
</TASK>
Allocated by task 5234:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
__kasan_kmalloc+0x98/0xb0 mm/kasan/common.c:394
kasan_kmalloc include/linux/kasan.h:260 [inline]
__do_kmalloc_node mm/slub.c:4273 [inline]
__kmalloc_node_track_caller_noprof+0x28b/0x4c0 mm/slub.c:4292
__do_krealloc mm/slub.c:4767 [inline]
krealloc_noprof+0x65/0x100 mm/slub.c:4816
bch2_sb_realloc+0x2d2/0x660 fs/bcachefs/super-io.c:189
__copy_super+0x5dc/0xe70 fs/bcachefs/super-io.c:586
bch2_sb_to_fs+0xab/0x150 fs/bcachefs/super-io.c:613
bch2_fs_alloc fs/bcachefs/super.c:828 [inline]
bch2_fs_open+0x16b2/0x2fa0 fs/bcachefs/super.c:2065
bch2_fs_get_tree+0x738/0x1710 fs/bcachefs/fs.c:2161
vfs_get_tree+0x90/0x2b0 fs/super.c:1814
do_new_mount+0x2be/0xb40 fs/namespace.c:3507
do_mount fs/namespace.c:3847 [inline]
__do_sys_mount fs/namespace.c:4055 [inline]
__se_sys_mount+0x2d6/0x3c0 fs/namespace.c:4032
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
Freed by task 5234:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:582
poison_slab_object mm/kasan/common.c:247 [inline]
__kasan_slab_free+0x59/0x70 mm/kasan/common.c:264
kasan_slab_free include/linux/kasan.h:233 [inline]
slab_free_hook mm/slub.c:2329 [inline]
slab_free mm/slub.c:4588 [inline]
kfree+0x1a0/0x460 mm/slub.c:4736
krealloc_noprof+0xc9/0x100
bch2_sb_realloc+0x2d2/0x660 fs/bcachefs/super-io.c:189
bch2_sb_field_resize_id+0x140/0x7c0 fs/bcachefs/super-io.c:221
bch2_sb_counters_from_cpu+0xac/0x300 fs/bcachefs/sb-counters.c:67
bch2_write_super+0xe80/0x3c50 fs/bcachefs/super-io.c:976
bch2_reconstruct_alloc+0x28c/0xac0 fs/bcachefs/recovery.c:131
bch2_fs_recovery+0x12dd/0x39a0 fs/bcachefs/recovery.c:842
bch2_fs_start+0x356/0x5b0 fs/bcachefs/super.c:1037
bch2_fs_get_tree+0xd68/0x1710 fs/bcachefs/fs.c:2174
vfs_get_tree+0x90/0x2b0 fs/super.c:1814
do_new_mount+0x2be/0xb40 fs/namespace.c:3507
do_mount fs/namespace.c:3847 [inline]
__do_sys_mount fs/namespace.c:4055 [inline]
__se_sys_mount+0x2d6/0x3c0 fs/namespace.c:4032
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
The buggy address belongs to the object at ffff888075728000
which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 3928 bytes inside of
freed 4096-byte region [ffff888075728000, ffff888075729000)
The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x75728
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801ac42140 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000040004 00000001f5000000 0000000000000000
head: 00fff00000000040 ffff88801ac42140 dead000000000122 0000000000000000
head: 0000000000000000 0000000000040004 00000001f5000000 0000000000000000
head: 00fff00000000003 ffffea0001d5ca01 ffffffffffffffff 0000000000000000
head: 0000000000000008 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd2040(__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5234, tgid 5234 (syz-executor251), ts 72141103867, free_ts 58943313114
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1537
prep_new_page mm/page_alloc.c:1545 [inline]
get_page_from_freelist+0x3123/0x3270 mm/page_alloc.c:3493
__alloc_pages_noprof+0x292/0x710 mm/page_alloc.c:4769
alloc_pages_mpol_noprof+0x3e8/0x680 mm/mempolicy.c:2265
alloc_slab_page+0x6a/0x120 mm/slub.c:2399
allocate_slab+0x5a/0x2f0 mm/slub.c:2565
new_slab mm/slub.c:2618 [inline]
___slab_alloc+0xcd1/0x14b0 mm/slub.c:3805
__slab_alloc+0x58/0xa0 mm/slub.c:3895
__slab_alloc_node mm/slub.c:3970 [inline]
slab_alloc_node mm/slub.c:4131 [inline]
__do_kmalloc_node mm/slub.c:4272 [inline]
__kmalloc_node_track_caller_noprof+0x2e9/0x4c0 mm/slub.c:4292
__do_krealloc mm/slub.c:4767 [inline]
krealloc_noprof+0x65/0x100 mm/slub.c:4816
bch2_sb_realloc+0x2d2/0x660 fs/bcachefs/super-io.c:189
__copy_super+0x5dc/0xe70 fs/bcachefs/super-io.c:586
bch2_sb_to_fs+0xab/0x150 fs/bcachefs/super-io.c:613
bch2_fs_alloc fs/bcachefs/super.c:828 [inline]
bch2_fs_open+0x16b2/0x2fa0 fs/bcachefs/super.c:2065
bch2_fs_get_tree+0x738/0x1710 fs/bcachefs/fs.c:2161
vfs_get_tree+0x90/0x2b0 fs/super.c:1814
page last free pid 5215 tgid 5215 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1108 [inline]
free_unref_page+0xcfb/0xf20 mm/page_alloc.c:2674
__folio_put+0x2c7/0x440 mm/swap.c:126
pipe_buf_release include/linux/pipe_fs_i.h:219 [inline]
pipe_update_tail fs/pipe.c:224 [inline]
pipe_read+0x6ed/0x13e0 fs/pipe.c:344
new_sync_read fs/read_write.c:488 [inline]
vfs_read+0x9bb/0xbc0 fs/read_write.c:569
ksys_read+0x183/0x2b0 fs/read_write.c:712
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
Memory state around the buggy address:
ffff888075728e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888075728e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888075728f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888075728f80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888075729000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
---
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syzbot will keep track of this issue. See:
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For information about bisection process see: https://goo.gl/tpsmEJ#bisection
If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.
If you want to overwrite report's subsystems, reply with:
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#syz undup
^ permalink raw reply [flat|nested] 7+ messages in thread* Re: [syzbot] [bcachefs?] KASAN: slab-use-after-free Read in bch2_reconstruct_alloc 2024-10-23 14:27 [syzbot] [bcachefs?] KASAN: slab-use-after-free Read in bch2_reconstruct_alloc syzbot @ 2024-10-25 10:02 ` Lizhi Xu 2024-10-25 10:31 ` syzbot 2024-10-26 1:09 ` [PATCH] bcachefs: Retrieve ext again after sb is reallocated Lizhi Xu 0 siblings, 2 replies; 7+ messages in thread From: Lizhi Xu @ 2024-10-25 10:02 UTC (permalink / raw) To: syzbot+9fc4dac4775d07bcfe34 Cc: bfoster, kent.overstreet, linux-bcachefs, linux-kernel, syzkaller-bugs The counters will cause sb to be realloc and release the old sb, which leads to uaf in ext #syz test: upstream master diff --git a/fs/bcachefs/recovery.c b/fs/bcachefs/recovery.c index 55e1504a8130..9df0969c29ce 100644 --- a/fs/bcachefs/recovery.c +++ b/fs/bcachefs/recovery.c @@ -59,6 +59,7 @@ static void bch2_reconstruct_alloc(struct bch_fs *c) mutex_lock(&c->sb_lock); struct bch_sb_field_ext *ext = bch2_sb_field_get(c->disk_sb.sb, ext); + void *sb; __set_bit_le64(BCH_RECOVERY_PASS_STABLE_check_allocations, ext->recovery_passes_required); __set_bit_le64(BCH_RECOVERY_PASS_STABLE_check_alloc_info, ext->recovery_passes_required); @@ -94,7 +95,10 @@ static void bch2_reconstruct_alloc(struct bch_fs *c) __set_bit_le64(BCH_FSCK_ERR_accounting_mismatch, ext->errors_silent); c->sb.compat &= ~(1ULL << BCH_COMPAT_alloc_info); + sb = c->disk_sb.sb; bch2_write_super(c); + if (sb != c->disk_sb.sb) + ext = bch2_sb_field_get(c->disk_sb.sb, ext); mutex_unlock(&c->sb_lock); c->opts.recovery_passes |= bch2_recovery_passes_from_stable(le64_to_cpu(ext->recovery_passes_required[0])); ^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [syzbot] [bcachefs?] KASAN: slab-use-after-free Read in bch2_reconstruct_alloc 2024-10-25 10:02 ` Lizhi Xu @ 2024-10-25 10:31 ` syzbot 2024-10-26 1:09 ` [PATCH] bcachefs: Retrieve ext again after sb is reallocated Lizhi Xu 1 sibling, 0 replies; 7+ messages in thread From: syzbot @ 2024-10-25 10:31 UTC (permalink / raw) To: bfoster, kent.overstreet, linux-bcachefs, linux-kernel, lizhi.xu, syzkaller-bugs Hello, syzbot has tested the proposed patch and the reproducer did not trigger any issue: Reported-by: syzbot+9fc4dac4775d07bcfe34@syzkaller.appspotmail.com Tested-by: syzbot+9fc4dac4775d07bcfe34@syzkaller.appspotmail.com Tested on: commit: ae90f6a6 Merge tag 'bpf-fixes' of git://git.kernel.org.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=11ab0230580000 kernel config: https://syzkaller.appspot.com/x/.config?x=fc6f8ce8c5369043 dashboard link: https://syzkaller.appspot.com/bug?extid=9fc4dac4775d07bcfe34 compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 patch: https://syzkaller.appspot.com/x/patch.diff?x=10530230580000 Note: testing is done by a robot and is best-effort only. ^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH] bcachefs: Retrieve ext again after sb is reallocated 2024-10-25 10:02 ` Lizhi Xu 2024-10-25 10:31 ` syzbot @ 2024-10-26 1:09 ` Lizhi Xu 2024-10-26 1:17 ` Kent Overstreet 1 sibling, 1 reply; 7+ messages in thread From: Lizhi Xu @ 2024-10-26 1:09 UTC (permalink / raw) To: lizhi.xu Cc: bfoster, kent.overstreet, linux-bcachefs, linux-kernel, syzbot+9fc4dac4775d07bcfe34, syzkaller-bugs Syzbot reported a slab-use-after-free Read in bch2_reconstruct_alloc. The sb counters resize will cause sb reallocation and release the old sb, which leads to uaf in ext. After disk_sb.sb is reallocated, ext should be retrieved again to avoid uaf. Reported-and-tested-by: syzbot+9fc4dac4775d07bcfe34@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=9fc4dac4775d07bcfe34 Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com> --- fs/bcachefs/recovery.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/fs/bcachefs/recovery.c b/fs/bcachefs/recovery.c index 55e1504a8130..9df0969c29ce 100644 --- a/fs/bcachefs/recovery.c +++ b/fs/bcachefs/recovery.c @@ -59,6 +59,7 @@ static void bch2_reconstruct_alloc(struct bch_fs *c) mutex_lock(&c->sb_lock); struct bch_sb_field_ext *ext = bch2_sb_field_get(c->disk_sb.sb, ext); + void *sb; __set_bit_le64(BCH_RECOVERY_PASS_STABLE_check_allocations, ext->recovery_passes_required); __set_bit_le64(BCH_RECOVERY_PASS_STABLE_check_alloc_info, ext->recovery_passes_required); @@ -94,7 +95,10 @@ static void bch2_reconstruct_alloc(struct bch_fs *c) __set_bit_le64(BCH_FSCK_ERR_accounting_mismatch, ext->errors_silent); c->sb.compat &= ~(1ULL << BCH_COMPAT_alloc_info); + sb = c->disk_sb.sb; bch2_write_super(c); + if (sb != c->disk_sb.sb) + ext = bch2_sb_field_get(c->disk_sb.sb, ext); mutex_unlock(&c->sb_lock); c->opts.recovery_passes |= bch2_recovery_passes_from_stable(le64_to_cpu(ext->recovery_passes_required[0])); -- 2.43.0 ^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH] bcachefs: Retrieve ext again after sb is reallocated 2024-10-26 1:09 ` [PATCH] bcachefs: Retrieve ext again after sb is reallocated Lizhi Xu @ 2024-10-26 1:17 ` Kent Overstreet 2024-10-26 4:19 ` Lizhi Xu 0 siblings, 1 reply; 7+ messages in thread From: Kent Overstreet @ 2024-10-26 1:17 UTC (permalink / raw) To: Lizhi Xu Cc: bfoster, linux-bcachefs, linux-kernel, syzbot+9fc4dac4775d07bcfe34, syzkaller-bugs On Sat, Oct 26, 2024 at 09:09:53AM +0800, Lizhi Xu wrote: > Syzbot reported a slab-use-after-free Read in bch2_reconstruct_alloc. > The sb counters resize will cause sb reallocation and release the old sb, > which leads to uaf in ext. > After disk_sb.sb is reallocated, ext should be retrieved again to avoid uaf. > > Reported-and-tested-by: syzbot+9fc4dac4775d07bcfe34@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=9fc4dac4775d07bcfe34 > Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com> > --- > fs/bcachefs/recovery.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/fs/bcachefs/recovery.c b/fs/bcachefs/recovery.c > index 55e1504a8130..9df0969c29ce 100644 > --- a/fs/bcachefs/recovery.c > +++ b/fs/bcachefs/recovery.c > @@ -59,6 +59,7 @@ static void bch2_reconstruct_alloc(struct bch_fs *c) > > mutex_lock(&c->sb_lock); > struct bch_sb_field_ext *ext = bch2_sb_field_get(c->disk_sb.sb, ext); > + void *sb; > > __set_bit_le64(BCH_RECOVERY_PASS_STABLE_check_allocations, ext->recovery_passes_required); > __set_bit_le64(BCH_RECOVERY_PASS_STABLE_check_alloc_info, ext->recovery_passes_required); > @@ -94,7 +95,10 @@ static void bch2_reconstruct_alloc(struct bch_fs *c) > __set_bit_le64(BCH_FSCK_ERR_accounting_mismatch, ext->errors_silent); > c->sb.compat &= ~(1ULL << BCH_COMPAT_alloc_info); > > + sb = c->disk_sb.sb; > bch2_write_super(c); > + if (sb != c->disk_sb.sb) > + ext = bch2_sb_field_get(c->disk_sb.sb, ext); > mutex_unlock(&c->sb_lock); > > c->opts.recovery_passes |= bch2_recovery_passes_from_stable(le64_to_cpu(ext->recovery_passes_required[0])); There's a simpler fix: From 8e910ca20e112d7f06ba3bf631a06ddb5ce14657 Mon Sep 17 00:00:00 2001 From: Kent Overstreet <kent.overstreet@linux.dev> Date: Fri, 25 Oct 2024 13:13:05 -0400 Subject: [PATCH] bcachefs: Fix UAF in bch2_reconstruct_alloc() write_super() -> sb_counters_from_cpu() may reallocate the superblock Reported-by: syzbot+9fc4dac4775d07bcfe34@syzkaller.appspotmail.com Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev> diff --git a/fs/bcachefs/recovery.c b/fs/bcachefs/recovery.c index 454b5a32dd7f..0ebc76dd7eb5 100644 --- a/fs/bcachefs/recovery.c +++ b/fs/bcachefs/recovery.c @@ -94,11 +94,10 @@ static void bch2_reconstruct_alloc(struct bch_fs *c) __set_bit_le64(BCH_FSCK_ERR_accounting_mismatch, ext->errors_silent); c->sb.compat &= ~(1ULL << BCH_COMPAT_alloc_info); - bch2_write_super(c); - mutex_unlock(&c->sb_lock); - c->opts.recovery_passes |= bch2_recovery_passes_from_stable(le64_to_cpu(ext->recovery_passes_required[0])); + bch2_write_super(c); + mutex_unlock(&c->sb_lock); bch2_shoot_down_journal_keys(c, BTREE_ID_alloc, 0, BTREE_MAX_DEPTH, POS_MIN, SPOS_MAX); ^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH] bcachefs: Retrieve ext again after sb is reallocated 2024-10-26 1:17 ` Kent Overstreet @ 2024-10-26 4:19 ` Lizhi Xu 2024-10-26 4:21 ` [syzbot] [bcachefs?] KASAN: slab-use-after-free Read in bch2_reconstruct_alloc syzbot 0 siblings, 1 reply; 7+ messages in thread From: Lizhi Xu @ 2024-10-26 4:19 UTC (permalink / raw) To: kent.overstreet Cc: bfoster, linux-bcachefs, linux-kernel, lizhi.xu, syzbot+9fc4dac4775d07bcfe34, syzkaller-bugs On Fri, 25 Oct 2024 21:17:09 -0400, Kent Overstreet wrote: > On Sat, Oct 26, 2024 at 09:09:53AM +0800, Lizhi Xu wrote: > > Syzbot reported a slab-use-after-free Read in bch2_reconstruct_alloc. > > The sb counters resize will cause sb reallocation and release the old sb, > > which leads to uaf in ext. > > After disk_sb.sb is reallocated, ext should be retrieved again to avoid uaf. > > > > Reported-and-tested-by: syzbot+9fc4dac4775d07bcfe34@syzkaller.appspotmail.com > > Closes: https://syzkaller.appspot.com/bug?extid=9fc4dac4775d07bcfe34 > > Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com> > > --- > > fs/bcachefs/recovery.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/fs/bcachefs/recovery.c b/fs/bcachefs/recovery.c > > index 55e1504a8130..9df0969c29ce 100644 > > --- a/fs/bcachefs/recovery.c > > +++ b/fs/bcachefs/recovery.c > > @@ -59,6 +59,7 @@ static void bch2_reconstruct_alloc(struct bch_fs *c) > > > > mutex_lock(&c->sb_lock); > > struct bch_sb_field_ext *ext = bch2_sb_field_get(c->disk_sb.sb, ext); > > + void *sb; > > > > __set_bit_le64(BCH_RECOVERY_PASS_STABLE_check_allocations, ext->recovery_passes_required); > > __set_bit_le64(BCH_RECOVERY_PASS_STABLE_check_alloc_info, ext->recovery_passes_required); > > @@ -94,7 +95,10 @@ static void bch2_reconstruct_alloc(struct bch_fs *c) > > __set_bit_le64(BCH_FSCK_ERR_accounting_mismatch, ext->errors_silent); > > c->sb.compat &= ~(1ULL << BCH_COMPAT_alloc_info); > > > > + sb = c->disk_sb.sb; > > bch2_write_super(c); > > + if (sb != c->disk_sb.sb) > > + ext = bch2_sb_field_get(c->disk_sb.sb, ext); > > mutex_unlock(&c->sb_lock); > > > > c->opts.recovery_passes |= bch2_recovery_passes_from_stable(le64_to_cpu(ext->recovery_passes_required[0])); > > There's a simpler fix: > > > From 8e910ca20e112d7f06ba3bf631a06ddb5ce14657 Mon Sep 17 00:00:00 2001 > From: Kent Overstreet <kent.overstreet@linux.dev> > Date: Fri, 25 Oct 2024 13:13:05 -0400 > Subject: [PATCH] bcachefs: Fix UAF in bch2_reconstruct_alloc() > > write_super() -> sb_counters_from_cpu() may reallocate the superblock > > Reported-by: syzbot+9fc4dac4775d07bcfe34@syzkaller.appspotmail.com > Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev> > > diff --git a/fs/bcachefs/recovery.c b/fs/bcachefs/recovery.c > index 454b5a32dd7f..0ebc76dd7eb5 100644 > --- a/fs/bcachefs/recovery.c > +++ b/fs/bcachefs/recovery.c > @@ -94,11 +94,10 @@ static void bch2_reconstruct_alloc(struct bch_fs *c) > __set_bit_le64(BCH_FSCK_ERR_accounting_mismatch, ext->errors_silent); > c->sb.compat &= ~(1ULL << BCH_COMPAT_alloc_info); > > - bch2_write_super(c); > - mutex_unlock(&c->sb_lock); > - > c->opts.recovery_passes |= bch2_recovery_passes_from_stable(le64_to_cpu(ext->recovery_passes_required[0])); > > + bch2_write_super(c); > + mutex_unlock(&c->sb_lock); > > bch2_shoot_down_journal_keys(c, BTREE_ID_alloc, > 0, BTREE_MAX_DEPTH, POS_MIN, SPOS_MAX); Oh, Yes, it can fix, but my first fix is before your patch, https://lore.kernel.org/all/20241025100205.635960-1-lizhi.xu@windriver.com/ Subject: Re: [syzbot] [bcachefs?] KASAN: slab-use-after-free Read in bch2_reconstruct_alloc Date: Fri, 25 Oct 2024 18:02:05 +0800 [thread overview] Message-ID: <20241025100205.635960-1-lizhi.xu@windriver.com> (raw) In-Reply-To: <671907d4.050a0220.1e4b4d.008f.GAE@google.com> The counters will cause sb to be realloc and release the old sb, which leads to uaf in ext #syz test: upstream master diff --git a/fs/bcachefs/recovery.c b/fs/bcachefs/recovery.c index 55e1504a8130..9df0969c29ce 100644 --- a/fs/bcachefs/recovery.c +++ b/fs/bcachefs/recovery.c @@ -59,6 +59,7 @@ static void bch2_reconstruct_alloc(struct bch_fs *c) mutex_lock(&c->sb_lock); struct bch_sb_field_ext *ext = bch2_sb_field_get(c->disk_sb.sb, ext); + void *sb; __set_bit_le64(BCH_RECOVERY_PASS_STABLE_check_allocations, ext->recovery_passes_required); __set_bit_le64(BCH_RECOVERY_PASS_STABLE_check_alloc_info, ext->recovery_passes_required); @@ -94,7 +95,10 @@ static void bch2_reconstruct_alloc(struct bch_fs *c) __set_bit_le64(BCH_FSCK_ERR_accounting_mismatch, ext->errors_silent); c->sb.compat &= ~(1ULL << BCH_COMPAT_alloc_info); + sb = c->disk_sb.sb; bch2_write_super(c); + if (sb != c->disk_sb.sb) + ext = bch2_sb_field_get(c->disk_sb.sb, ext); mutex_unlock(&c->sb_lock); c->opts.recovery_passes |= bch2_recovery_passes_from_stable(le64_to_cpu(ext->recovery_passes_required[0])); ^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [syzbot] [bcachefs?] KASAN: slab-use-after-free Read in bch2_reconstruct_alloc 2024-10-26 4:19 ` Lizhi Xu @ 2024-10-26 4:21 ` syzbot 0 siblings, 0 replies; 7+ messages in thread From: syzbot @ 2024-10-26 4:21 UTC (permalink / raw) To: bfoster, kent.overstreet, linux-bcachefs, linux-kernel, lizhi.xu, syzkaller-bugs Hello, syzbot tried to test the proposed patch but the build/boot failed: failed to apply patch: checking file fs/bcachefs/recovery.c patch: **** unexpected end of file in patch Tested on: commit: 850925a8 Merge tag '9p-for-6.12-rc5' of https://github.. git tree: upstream kernel config: https://syzkaller.appspot.com/x/.config?x=c36416f1c54640c0 dashboard link: https://syzkaller.appspot.com/bug?extid=9fc4dac4775d07bcfe34 compiler: patch: https://syzkaller.appspot.com/x/patch.diff?x=11c57287980000 ^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2024-10-26 4:21 UTC | newest] Thread overview: 7+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2024-10-23 14:27 [syzbot] [bcachefs?] KASAN: slab-use-after-free Read in bch2_reconstruct_alloc syzbot 2024-10-25 10:02 ` Lizhi Xu 2024-10-25 10:31 ` syzbot 2024-10-26 1:09 ` [PATCH] bcachefs: Retrieve ext again after sb is reallocated Lizhi Xu 2024-10-26 1:17 ` Kent Overstreet 2024-10-26 4:19 ` Lizhi Xu 2024-10-26 4:21 ` [syzbot] [bcachefs?] KASAN: slab-use-after-free Read in bch2_reconstruct_alloc syzbot
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