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authorJohannes Thumshirn <johannes.thumshirn@wdc.com>2020-09-21 10:57:14 +0300
committerDavid Sterba <dsterba@suse.com>2020-09-21 13:39:21 +0300
commit35be8851d172c6e3db836c0f28c19087b10c9e00 (patch)
tree4c7695e38373401ca4502eec9c2f01edad1bd399 /fs
parent1c78544eaa4660096aeb6a57ec82b42cdb3bfe5a (diff)
downloadlinux-35be8851d172c6e3db836c0f28c19087b10c9e00.tar.xz
btrfs: fix overflow when copying corrupt csums for a message
Syzkaller reported a buffer overflow in btree_readpage_end_io_hook() when loop mounting a crafted image: detected buffer overflow in memcpy ------------[ cut here ]------------ kernel BUG at lib/string.c:1129! invalid opcode: 0000 [#1] PREEMPT SMP KASAN CPU: 1 PID: 26 Comm: kworker/u4:2 Not tainted 5.9.0-rc4-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: btrfs-endio-meta btrfs_work_helper RIP: 0010:fortify_panic+0xf/0x20 lib/string.c:1129 RSP: 0018:ffffc90000e27980 EFLAGS: 00010286 RAX: 0000000000000022 RBX: ffff8880a80dca64 RCX: 0000000000000000 RDX: ffff8880a90860c0 RSI: ffffffff815dba07 RDI: fffff520001c4f22 RBP: ffff8880a80dca00 R08: 0000000000000022 R09: ffff8880ae7318e7 R10: 0000000000000000 R11: 0000000000077578 R12: 00000000ffffff6e R13: 0000000000000008 R14: ffffc90000e27a40 R15: 1ffff920001c4f3c FS: 0000000000000000(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000557335f440d0 CR3: 000000009647d000 CR4: 00000000001506e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: memcpy include/linux/string.h:405 [inline] btree_readpage_end_io_hook.cold+0x206/0x221 fs/btrfs/disk-io.c:642 end_bio_extent_readpage+0x4de/0x10c0 fs/btrfs/extent_io.c:2854 bio_endio+0x3cf/0x7f0 block/bio.c:1449 end_workqueue_fn+0x114/0x170 fs/btrfs/disk-io.c:1695 btrfs_work_helper+0x221/0xe20 fs/btrfs/async-thread.c:318 process_one_work+0x94c/0x1670 kernel/workqueue.c:2269 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415 kthread+0x3b5/0x4a0 kernel/kthread.c:292 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294 Modules linked in: ---[ end trace b68924293169feef ]--- RIP: 0010:fortify_panic+0xf/0x20 lib/string.c:1129 RSP: 0018:ffffc90000e27980 EFLAGS: 00010286 RAX: 0000000000000022 RBX: ffff8880a80dca64 RCX: 0000000000000000 RDX: ffff8880a90860c0 RSI: ffffffff815dba07 RDI: fffff520001c4f22 RBP: ffff8880a80dca00 R08: 0000000000000022 R09: ffff8880ae7318e7 R10: 0000000000000000 R11: 0000000000077578 R12: 00000000ffffff6e R13: 0000000000000008 R14: ffffc90000e27a40 R15: 1ffff920001c4f3c FS: 0000000000000000(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f95b7c4d008 CR3: 000000009647d000 CR4: 00000000001506e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 The overflow happens, because in btree_readpage_end_io_hook() we assume that we have found a 4 byte checksum instead of the real possible 32 bytes we have for the checksums. With the fix applied: [ 35.726623] BTRFS: device fsid 815caf9a-dc43-4d2a-ac54-764b8333d765 devid 1 transid 5 /dev/loop0 scanned by syz-repro (215) [ 35.738994] BTRFS info (device loop0): disk space caching is enabled [ 35.738998] BTRFS info (device loop0): has skinny extents [ 35.743337] BTRFS warning (device loop0): loop0 checksum verify failed on 1052672 wanted 0xf9c035fc8d239a54 found 0x67a25c14b7eabcf9 level 0 [ 35.743420] BTRFS error (device loop0): failed to read chunk root [ 35.745899] BTRFS error (device loop0): open_ctree failed Reported-by: syzbot+e864a35d361e1d4e29a5@syzkaller.appspotmail.com Fixes: d5178578bcd4 ("btrfs: directly call into crypto framework for checksumming") CC: stable@vger.kernel.org # 5.4+ Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs')
-rw-r--r--fs/btrfs/disk-io.c11
1 files changed, 5 insertions, 6 deletions
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 9fe9ec6aab71..93d3bb8989df 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -636,16 +636,15 @@ static int btree_readpage_end_io_hook(struct btrfs_io_bio *io_bio,
csum_tree_block(eb, result);
if (memcmp_extent_buffer(eb, result, 0, csum_size)) {
- u32 val;
- u32 found = 0;
-
- memcpy(&found, result, csum_size);
+ u8 val[BTRFS_CSUM_SIZE] = { 0 };
read_extent_buffer(eb, &val, 0, csum_size);
btrfs_warn_rl(fs_info,
- "%s checksum verify failed on %llu wanted %x found %x level %d",
+ "%s checksum verify failed on %llu wanted " CSUM_FMT " found " CSUM_FMT " level %d",
fs_info->sb->s_id, eb->start,
- val, found, btrfs_header_level(eb));
+ CSUM_FMT_VALUE(csum_size, val),
+ CSUM_FMT_VALUE(csum_size, result),
+ btrfs_header_level(eb));
ret = -EUCLEAN;
goto err;
}