KMSAN: uninit-value in get_block

From: syzbot
Date: Wed May 20 2020 - 14:23:26 EST

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Hello,

syzbot found the following crash on:

HEAD commit: 8b97c627 kmsan: drop the opportunity to ignore pages
git tree: https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=17f2e73a100000
kernel config: https://syzkaller.appspot.com/x/.config?x=6f048d804e1a47a0
dashboard link: https://syzkaller.appspot.com/bug?extid=6e056ee473568865f3e6
compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
userspace arch: i386
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13cd424a100000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1213334e100000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+6e056ee473568865f3e6@xxxxxxxxxxxxxxxxxxxxxxxxx

Process accounting resumed
=====================================================
BUG: KMSAN: uninit-value in get_branch fs/minix/itree_common.c:54 [inline]
BUG: KMSAN: uninit-value in get_block+0xa00/0x1f80 fs/minix/itree_common.c:160
CPU: 0 PID: 8783 Comm: syz-executor148 Not tainted 5.7.0-rc4-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+0x1c9/0x220 lib/dump_stack.c:118
kmsan_report+0xf7/0x1e0 mm/kmsan/kmsan_report.c:121
__msan_warning+0x58/0xa0 mm/kmsan/kmsan_instr.c:215
get_branch fs/minix/itree_common.c:54 [inline]
get_block+0xa00/0x1f80 fs/minix/itree_common.c:160
V1_minix_get_block+0xb5/0xd0 fs/minix/itree_v1.c:56
minix_get_block+0x13e/0x1f0 fs/minix/inode.c:376
__block_write_begin_int+0xb05/0x2ad0 fs/buffer.c:2013
__block_write_begin fs/buffer.c:2063 [inline]
block_write_begin+0x16c/0x340 fs/buffer.c:2122
minix_write_begin+0x119/0x3d0 fs/minix/inode.c:412
generic_perform_write+0x3d4/0x9a0 mm/filemap.c:3302
__generic_file_write_iter+0x44e/0xa50 mm/filemap.c:3431
generic_file_write_iter+0x770/0xad0 mm/filemap.c:3463
call_write_iter include/linux/fs.h:1907 [inline]
new_sync_write fs/read_write.c:484 [inline]
__vfs_write+0xa5a/0xca0 fs/read_write.c:497
__kernel_write+0x205/0x600 fs/read_write.c:516
do_acct_process+0x1b6a/0x1fb0 kernel/acct.c:522
acct_pin_kill+0x54/0x250 kernel/acct.c:174
pin_kill+0x1c8/0x5d0 fs/fs_pin.c:44
acct_on kernel/acct.c:254 [inline]
__do_sys_acct kernel/acct.c:286 [inline]
__se_sys_acct+0xbcd/0xdd0 kernel/acct.c:273
__ia32_sys_acct+0x32/0x50 kernel/acct.c:273
do_syscall_32_irqs_on arch/x86/entry/common.c:339 [inline]
do_fast_syscall_32+0x3bf/0x6d0 arch/x86/entry/common.c:398
entry_SYSENTER_compat+0x68/0x77 arch/x86/entry/entry_64_compat.S:139
RIP: 0023:0xf7fb7dd9
Code: 90 e8 0b 00 00 00 f3 90 0f ae e8 eb f9 8d 74 26 00 89 3c 24 c3 90 90 90 90 90 90 90 90 90 90 90 90 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90
RSP: 002b:00000000f7f9112c EFLAGS: 00000292 ORIG_RAX: 0000000000000033
RAX: ffffffffffffffda RBX: 0000000020000480 RCX: 0000000000000081
RDX: 00000000000f4240 RSI: 0000000000000000 RDI: 00000000080fbff0
RBP: 00000000080fbffc R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

Uninit was stored to memory at:
kmsan_save_stack_with_flags mm/kmsan/kmsan.c:144 [inline]
kmsan_internal_chain_origin+0xad/0x130 mm/kmsan/kmsan.c:310
__msan_chain_origin+0x50/0x90 mm/kmsan/kmsan_instr.c:165
add_chain fs/minix/itree_common.c:14 [inline]
get_branch fs/minix/itree_common.c:52 [inline]
get_block+0xa4d/0x1f80 fs/minix/itree_common.c:160
V1_minix_get_block+0xb5/0xd0 fs/minix/itree_v1.c:56
minix_get_block+0x13e/0x1f0 fs/minix/inode.c:376
__block_write_begin_int+0xb05/0x2ad0 fs/buffer.c:2013
__block_write_begin fs/buffer.c:2063 [inline]
block_write_begin+0x16c/0x340 fs/buffer.c:2122
minix_write_begin+0x119/0x3d0 fs/minix/inode.c:412
generic_perform_write+0x3d4/0x9a0 mm/filemap.c:3302
__generic_file_write_iter+0x44e/0xa50 mm/filemap.c:3431
generic_file_write_iter+0x770/0xad0 mm/filemap.c:3463
call_write_iter include/linux/fs.h:1907 [inline]
new_sync_write fs/read_write.c:484 [inline]
__vfs_write+0xa5a/0xca0 fs/read_write.c:497
__kernel_write+0x205/0x600 fs/read_write.c:516
do_acct_process+0x1b6a/0x1fb0 kernel/acct.c:522
acct_pin_kill+0x54/0x250 kernel/acct.c:174
pin_kill+0x1c8/0x5d0 fs/fs_pin.c:44
acct_on kernel/acct.c:254 [inline]
__do_sys_acct kernel/acct.c:286 [inline]
__se_sys_acct+0xbcd/0xdd0 kernel/acct.c:273
__ia32_sys_acct+0x32/0x50 kernel/acct.c:273
do_syscall_32_irqs_on arch/x86/entry/common.c:339 [inline]
do_fast_syscall_32+0x3bf/0x6d0 arch/x86/entry/common.c:398
entry_SYSENTER_compat+0x68/0x77 arch/x86/entry/entry_64_compat.S:139

Uninit was created at:
kmsan_save_stack_with_flags+0x3c/0x90 mm/kmsan/kmsan.c:144
kmsan_internal_alloc_meta_for_pages mm/kmsan/kmsan_shadow.c:269 [inline]
kmsan_alloc_page+0xb9/0x180 mm/kmsan/kmsan_shadow.c:293
__alloc_pages_nodemask+0x56a2/0x5dc0 mm/page_alloc.c:4848
alloc_pages_current+0x67d/0x990 mm/mempolicy.c:2295
alloc_pages include/linux/gfp.h:540 [inline]
__page_cache_alloc+0x95/0x310 mm/filemap.c:959
pagecache_get_page+0xab7/0x1250 mm/filemap.c:1645
find_or_create_page include/linux/pagemap.h:308 [inline]
grow_dev_page fs/buffer.c:983 [inline]
grow_buffers fs/buffer.c:1052 [inline]
__getblk_slow fs/buffer.c:1079 [inline]
__getblk_gfp+0x4bb/0xfc0 fs/buffer.c:1356
__bread_gfp+0xb9/0x670 fs/buffer.c:1401
sb_bread include/linux/buffer_head.h:309 [inline]
get_branch fs/minix/itree_common.c:46 [inline]
get_block+0x73e/0x1f80 fs/minix/itree_common.c:160
V1_minix_get_block+0xb5/0xd0 fs/minix/itree_v1.c:56
minix_get_block+0x13e/0x1f0 fs/minix/inode.c:376
__block_write_begin_int+0xb05/0x2ad0 fs/buffer.c:2013
__block_write_begin fs/buffer.c:2063 [inline]
block_write_begin+0x16c/0x340 fs/buffer.c:2122
minix_write_begin+0x119/0x3d0 fs/minix/inode.c:412
generic_perform_write+0x3d4/0x9a0 mm/filemap.c:3302
__generic_file_write_iter+0x44e/0xa50 mm/filemap.c:3431
generic_file_write_iter+0x770/0xad0 mm/filemap.c:3463
call_write_iter include/linux/fs.h:1907 [inline]
new_sync_write fs/read_write.c:484 [inline]
__vfs_write+0xa5a/0xca0 fs/read_write.c:497
__kernel_write+0x205/0x600 fs/read_write.c:516
do_acct_process+0x1b6a/0x1fb0 kernel/acct.c:522
acct_pin_kill+0x54/0x250 kernel/acct.c:174
pin_kill+0x1c8/0x5d0 fs/fs_pin.c:44
acct_on kernel/acct.c:254 [inline]
__do_sys_acct kernel/acct.c:286 [inline]
__se_sys_acct+0xbcd/0xdd0 kernel/acct.c:273
__ia32_sys_acct+0x32/0x50 kernel/acct.c:273
do_syscall_32_irqs_on arch/x86/entry/common.c:339 [inline]
do_fast_syscall_32+0x3bf/0x6d0 arch/x86/entry/common.c:398
entry_SYSENTER_compat+0x68/0x77 arch/x86/entry/entry_64_compat.S:139
=====================================================

---
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