Re: WARNING in iomap_apply

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Sat, Apr 11, 2020 at 05:25:58PM +0800, Hillf Danton wrote:
> 
> On Sat, 11 Apr 2020 00:39:13 -0700
> > syzbot found the following crash on:
> > 
> > HEAD commit:    7e634208 Merge tag 'acpi-5.7-rc1-2' of git://git.kernel.or..
> > git tree:       upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=127ebeb3e00000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=12205d036cec317f
> > dashboard link: https://syzkaller.appspot.com/bug?extid=77fa5bdb65cc39711820
> > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1196f257e00000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14c336c7e00000
> > 
> > The bug was bisected to:
> > 
> > commit d3b6f23f71670007817a5d59f3fbafab2b794e8c
> > Author: Ritesh Harjani <riteshh@linux.ibm.com>
> > Date:   Fri Feb 28 09:26:58 2020 +0000
> > 
> >     ext4: move ext4_fiemap to use iomap framework
> > 
> > bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=16c62a57e00000
> > final crash:    https://syzkaller.appspot.com/x/report.txt?x=15c62a57e00000
> > console output: https://syzkaller.appspot.com/x/log.txt?x=11c62a57e00000
> > 
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+77fa5bdb65cc39711820@syzkaller.appspotmail.com
> > Fixes: d3b6f23f7167 ("ext4: move ext4_fiemap to use iomap framework")
> > 
> > ------------[ cut here ]------------
> > WARNING: CPU: 0 PID: 7023 at fs/iomap/apply.c:51 iomap_apply+0xa0c/0xcb0 fs/iomap/apply.c:51
> > Kernel panic - not syncing: panic_on_warn set ...
> > CPU: 0 PID: 7023 Comm: syz-executor296 Not tainted 5.6.0-syzkaller #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> > Call Trace:
> >  __dump_stack lib/dump_stack.c:77 [inline]
> >  dump_stack+0x188/0x20d lib/dump_stack.c:118
> >  panic+0x2e3/0x75c kernel/panic.c:221
> >  __warn.cold+0x2f/0x35 kernel/panic.c:582
> >  report_bug+0x27b/0x2f0 lib/bug.c:195
> >  fixup_bug arch/x86/kernel/traps.c:175 [inline]
> >  fixup_bug arch/x86/kernel/traps.c:170 [inline]
> >  do_error_trap+0x12b/0x220 arch/x86/kernel/traps.c:267
> >  do_invalid_op+0x32/0x40 arch/x86/kernel/traps.c:286
> >  invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1027
> > RIP: 0010:iomap_apply+0xa0c/0xcb0 fs/iomap/apply.c:51
> > Code: ff e9 0e fd ff ff e8 23 30 96 ff 0f 0b e9 07 f7 ff ff e8 17 30 96 ff 0f 0b 49 c7 c4 fb ff ff ff e9 35 f9 ff ff e8 04 30 96 ff <0f> 0b 49 c7 c4 fb ff ff ff e9 22 f9 ff ff e8 f1 2f 96 ff 0f 0b e9
> > RSP: 0018:ffffc90000f87968 EFLAGS: 00010293
> > RAX: ffff8880a1b00480 RBX: ffffc90000f879c8 RCX: ffffffff81dcf934
> > RDX: 0000000000000000 RSI: ffffffff81dd016c RDI: 0000000000000007
> > RBP: 0000000000000000 R08: ffff8880a1b00480 R09: ffffed1015cc70fc
> > R10: ffff8880ae6387db R11: ffffed1015cc70fb R12: 0000000000000000
> > R13: ffff888085e716b8 R14: 0000000000000000 R15: ffffc90000f87b50
> >  iomap_fiemap+0x184/0x2c0 fs/iomap/fiemap.c:88
> >  _ext4_fiemap+0x178/0x4f0 fs/ext4/extents.c:4860
> >  ovl_fiemap+0x13f/0x200 fs/overlayfs/inode.c:467
> >  ioctl_fiemap fs/ioctl.c:226 [inline]
> >  do_vfs_ioctl+0x8d7/0x12d0 fs/ioctl.c:715
> >  ksys_ioctl+0xa3/0x180 fs/ioctl.c:761
> >  __do_sys_ioctl fs/ioctl.c:772 [inline]
> >  __se_sys_ioctl fs/ioctl.c:770 [inline]
> >  __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:770
> >  do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
> >  entry_SYSCALL_64_after_hwframe+0x49/0xb3
> 
> Check out-of-bound parameters.

No SOB, this patch cannot be taken.

> --- a/fs/iomap/fiemap.c
> +++ b/fs/iomap/fiemap.c
> @@ -70,6 +70,9 @@ int iomap_fiemap(struct inode *inode, st
>  	struct fiemap_ctx ctx;
>  	loff_t ret;
>  
> +	if (start < 0 || len < 0)
> +		return -EINVAL;

FIEMAP parameters ought to be range-checked in ioctl_fiemap().

--D

> +
>  	memset(&ctx, 0, sizeof(ctx));
>  	ctx.fi = fi;
>  	ctx.prev.type = IOMAP_HOLE;
>