Re: UBSAN: shift-out-of-bounds in extAlloc

[Hao Sun]

Hi,

This bug can still be triggered repeatedly on the latest Linux.

HEAD commit: 519d81956ee2 Linux 5.15-rc6
git tree: upstream
console output:
kernel config: https://drive.google.com/file/d/12PUnxIM1EPBgW4ZJmI7WJBRaY1lA83an/view?usp=sharing
Syzlang reproducer:
https://drive.google.com/file/d/1658MoTb5EbxCtbsoI--hNQLab0HogUWf/view?usp=sharing

loop13: detected capacity change from 0 to 65534
================================================================================
UBSAN: shift-out-of-bounds in fs/jfs/jfs_extent.c:511:16
shift exponent -1 is negative
CPU: 2 PID: 31142 Comm: syz-executor Not tainted 5.15.0-rc6 #4
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
1.13.0-1ubuntu1.1 04/01/2014
Call Trace:
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
ubsan_epilogue+0xb/0x5a lib/ubsan.c:151
__ubsan_handle_shift_out_of_bounds.cold+0x76/0x144 lib/ubsan.c:330
extBalloc fs/jfs/jfs_extent.c:511 [inline]
extAlloc.cold+0x1a/0x92 fs/jfs/jfs_extent.c:125
jfs_get_block+0x662/0xaa0 fs/jfs/inode.c:257
get_more_blocks fs/direct-io.c:673 [inline]
do_direct_IO fs/direct-io.c:959 [inline]
do_blockdev_direct_IO+0x129e/0x6ce0 fs/direct-io.c:1276
blockdev_direct_IO include/linux/fs.h:3272 [inline]
jfs_direct_IO+0x10a/0x2c0 fs/jfs/inode.c:342
generic_file_direct_write+0x1e3/0x4c0 mm/filemap.c:3672
__generic_file_write_iter+0x2d3/0x640 mm/filemap.c:3854
generic_file_write_iter+0xd7/0x220 mm/filemap.c:3929
call_write_iter include/linux/fs.h:2163 [inline]
do_iter_readv_writev+0x47b/0x750 fs/read_write.c:729
do_iter_write fs/read_write.c:855 [inline]
do_iter_write+0x18b/0x700 fs/read_write.c:836
vfs_iter_write+0x70/0xa0 fs/read_write.c:896
iter_file_splice_write+0x723/0xbf0 fs/splice.c:689
do_splice_from fs/splice.c:767 [inline]
direct_splice_actor+0x110/0x180 fs/splice.c:936
splice_direct_to_actor+0x34b/0x8c0 fs/splice.c:891
do_splice_direct+0x1b3/0x280 fs/splice.c:979
do_sendfile+0xab6/0x1240 fs/read_write.c:1249
__do_sys_sendfile64 fs/read_write.c:1314 [inline]
__se_sys_sendfile64 fs/read_write.c:1300 [inline]
__x64_sys_sendfile64+0x1cc/0x210 fs/read_write.c:1300
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: 0033:0x7f8d8f6f5c4d
Code: 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa 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 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f8d8cc5dc58 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007f8d8f81c0a0 RCX: 00007f8d8f6f5c4d
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 0000000000000007
RBP: 00007f8d8f76ed80 R08: 0000000000000000 R09: 0000000000000000
R10: 00008400fffffffb R11: 0000000000000246 R12: 00007f8d8f81c0a0
R13: 00007ffea1a878ff R14: 00007ffea1a87aa0 R15: 00007f8d8cc5ddc0
================================================================================