Re: [syzbot] kernel BUG in ext4_ind_remove_space

Tadeusz Struk
2022-03-15T19:21:44Z

On 3/15/22 08:14, syzbot wrote:
> syzbot has found a reproducer for the following issue on:
>
> HEAD commit: 09688c0166e7 Linux 5.17-rc8
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=11a8bd61700000
> kernel config: https://syzkaller.appspot.com/x/.config?x=d35f9bc6884af6c9
> dashboard link: https://syzkaller.appspot.com/bug?extid=fcc629d1a1ae8d3fe8a5
> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1205b189700000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15dda4fe700000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+fcc629d1a1ae8d3fe8a5@syzkaller.appspotmail.com
>
> EXT4-fs warning (device sda1): ext4_block_to_path:105: block 1074791436 > max in inode 1137
> ------------[ cut here ]------------
> kernel BUG at fs/ext4/indirect.c:1244!
> invalid opcode: 0000 [#1] PREEMPT SMP KASAN
> CPU: 0 PID: 3590 Comm: syz-executor391 Not tainted 5.17.0-rc8-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> RIP: 0010:ext4_ind_remove_space+0xfde/0x1400 fs/ext4/indirect.c:1244
> Code: 00 0f 85 36 03 00 00 48 8b 0b 4c 89 fe 44 8b 4c 24 20 48 8b 7c 24 10 48 83 c1 04 e8 3c bb ff ff e9 02 f6 ff ff e8 c2 26 66 ff <0f> 0b 4c 8b 7c 24 50 e9 8e f9 ff ff e8 b1 26 66 ff 48 8b 7c 24 10
> RSP: 0018:ffffc90001adfab8 EFLAGS: 00010293
> RAX: 0000000000000000 RBX: 0000000000000001 RCX: 0000000000000000
> RDX: ffff888021523a00 RSI: ffffffff8212996e RDI: 0000000000000003
> RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000
> R10: ffffffff82128bea R11: 0000000000000000 R12: 0000000000001000
> R13: ffffc90001adfb68 R14: ffffc90001adfb88 R15: ffff8880751fa088
> FS: 00007f69922ff700(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000020000080 CR3: 0000000021605000 CR4: 0000000000350ef0
> Call Trace:
> <TASK>
> ext4_punch_hole+0xfe8/0x11d0 fs/ext4/inode.c:4044
> ext4_fallocate+0x1194/0x3ed0 fs/ext4/extents.c:4694
> vfs_fallocate+0x48d/0xe10 fs/open.c:308
> ksys_fallocate fs/open.c:331 [inline]
> __do_sys_fallocate fs/open.c:339 [inline]
> __se_sys_fallocate fs/open.c:337 [inline]
> __x64_sys_fallocate+0xcf/0x140 fs/open.c:337
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x7f699234cdf9
> Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 81 14 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007f69922ff308 EFLAGS: 00000246 ORIG_RAX: 000000000000011d
> RAX: ffffffffffffffda RBX: 0000000000000040 RCX: 00007f699234cdf9
> RDX: 0000000000000000 RSI: 0000000000000003 RDI: 0000000000000005
> RBP: 00007f69923d5408 R08: 0000000000000000 R09: 0000000000000000
> R10: 00000ffeffeff000 R11: 0000000000000246 R12: 00000ffeffeff000
> R13: 00007f69923d5400 R14: 00007f69923a3004 R15: 0000000000022000
> </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:ext4_ind_remove_space+0xfde/0x1400 fs/ext4/indirect.c:1244
> Code: 00 0f 85 36 03 00 00 48 8b 0b 4c 89 fe 44 8b 4c 24 20 48 8b 7c 24 10 48 83 c1 04 e8 3c bb ff ff e9 02 f6 ff ff e8 c2 26 66 ff <0f> 0b 4c 8b 7c 24 50 e9 8e f9 ff ff e8 b1 26 66 ff 48 8b 7c 24 10
> RSP: 0018:ffffc90001adfab8 EFLAGS: 00010293
> RAX: 0000000000000000 RBX: 0000000000000001 RCX: 0000000000000000
> RDX: ffff888021523a00 RSI: ffffffff8212996e RDI: 0000000000000003
> RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000
> R10: ffffffff82128bea R11: 0000000000000000 R12: 0000000000001000
> R13: ffffc90001adfb68 R14: ffffc90001adfb88 R15: ffff8880751fa088
> FS: 00007f69922ff700(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000020000080 CR3: 0000000021605000 CR4: 0000000000350ef0
>

#syz test:
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

===========================
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 01c9e4f743ba..dd9c35113efe 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3924,7 +3924,8 @@ int ext4_punch_hole(struct inode *inode, loff_t offset,
loff_t length)
struct super_block *sb = inode->i_sb;
ext4_lblk_t first_block, stop_block;
struct address_space *mapping = inode->i_mapping;
- loff_t first_block_offset, last_block_offset;
+ loff_t first_block_offset, last_block_offset, max_length;
+ struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
handle_t *handle;
unsigned int credits;
int ret = 0, ret2 = 0;
@@ -3967,6 +3968,16 @@ int ext4_punch_hole(struct inode *inode, loff_t offset,
loff_t length)
offset;
}

+ /*
+ * For punch hole the length + offset needs to be at least within
+ * one block before last
+ */
+ max_length = sbi->s_bitmap_maxbytes - sbi->s_blocksize;
+ if (offset + length >= max_length) {
+ ret = -ENOSPC;
+ goto out_mutex;
+ }
+
if (offset & (sb->s_blocksize - 1) ||
(offset + length) & (sb->s_blocksize - 1)) {
/*
--
Thanks,
Tadeusz