[PATCH v1] jfs: Fix uninit-value access of new_ea in ea_buffer

[Zhao Mengmeng]

syzbot reports that lzo1x_1_do_compress is using uninit-value:

=====================================================
BUG: KMSAN: uninit-value in lzo1x_1_do_compress+0x19f9/0x2510 lib/lzo/lzo1x_compress.c:178
 lzo1x_1_do_compress+0x19f9/0x2510 lib/lzo/lzo1x_compress.c:178
 lzogeneric1x_1_compress+0x26a/0x11b0 lib/lzo/lzo1x_compress.c:333
 lzo1x_1_compress+0x47/0x80 lib/lzo/lzo1x_compress.c:383
 __lzo_compress crypto/lzo.c:58 [inline]
 lzo_scompress+0x98/0x180 crypto/lzo.c:79
 scomp_acomp_comp_decomp+0x7c6/0xb90
 scomp_acomp_compress+0x32/0x40 crypto/scompress.c:187
 crypto_acomp_compress include/crypto/acompress.h:251 [inline]
 zswap_compress+0x368/0xad0 mm/zswap.c:927
 zswap_store+0x1af3/0x2dd0 mm/zswap.c:1459
 swap_writepage+0x11f/0x470 mm/page_io.c:198
 shmem_writepage+0x1a75/0x1f70 mm/shmem.c:1536
 pageout mm/vmscan.c:680 [inline]
 shrink_folio_list+0x577f/0x7cb0 mm/vmscan.c:1360
 evict_folios+0x9bce/0xbc80 mm/vmscan.c:4580
 try_to_shrink_lruvec+0x13a3/0x1750 mm/vmscan.c:4775
 shrink_one+0x646/0xd20 mm/vmscan.c:4813
 shrink_many mm/vmscan.c:4876 [inline]
 lru_gen_shrink_node mm/vmscan.c:4954 [inline]
 shrink_node+0x451a/0x50f0 mm/vmscan.c:5934
 kswapd_shrink_node mm/vmscan.c:6762 [inline]
 balance_pgdat mm/vmscan.c:6954 [inline]
 kswapd+0x257e/0x4290 mm/vmscan.c:7223
 kthread+0x3dd/0x540 kernel/kthread.c:389
 ret_from_fork+0x6d/0x90 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Uninit was stored to memory at:
 memcpy_from_iter lib/iov_iter.c:73 [inline]
 iterate_bvec include/linux/iov_iter.h:122 [inline]
 iterate_and_advance2 include/linux/iov_iter.h:249 [inline]
 iterate_and_advance include/linux/iov_iter.h:271 [inline]
 __copy_from_iter lib/iov_iter.c:249 [inline]
 copy_page_from_iter_atomic+0x12bb/0x2ae0 lib/iov_iter.c:481
 copy_folio_from_iter_atomic include/linux/uio.h:186 [inline]
 generic_perform_write+0x896/0x12e0 mm/filemap.c:4032
 shmem_file_write_iter+0x2bd/0x2f0 mm/shmem.c:3074
 do_iter_readv_writev+0x8a1/0xa40
 vfs_iter_write+0x459/0xd50 fs/read_write.c:895
 lo_write_bvec drivers/block/loop.c:243 [inline]
 lo_write_simple drivers/block/loop.c:264 [inline]
 do_req_filebacked drivers/block/loop.c:511 [inline]
 loop_handle_cmd drivers/block/loop.c:1910 [inline]
 loop_process_work+0x15ec/0x3750 drivers/block/loop.c:1945
 loop_rootcg_workfn+0x2b/0x40 drivers/block/loop.c:1976
 process_one_work kernel/workqueue.c:3231 [inline]
 process_scheduled_works+0xae0/0x1c40 kernel/workqueue.c:3312
 worker_thread+0xea7/0x14d0 kernel/workqueue.c:3389
 kthread+0x3dd/0x540 kernel/kthread.c:389
 ret_from_fork+0x6d/0x90 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Uninit was stored to memory at:
 copy_to_dinode+0x881/0xb30 fs/jfs/jfs_imap.c:3158
 diWrite+0x1bf5/0x1f00 fs/jfs/jfs_imap.c:790
 txCommit+0xdb8/0x8cd0 fs/jfs/jfs_txnmgr.c:1255
 __jfs_xattr_set+0x1b7/0x1f0 fs/jfs/xattr.c:936
 jfs_xattr_set+0x79/0x90 fs/jfs/xattr.c:958
 __vfs_setxattr+0x844/0x8b0 fs/xattr.c:200
 __vfs_setxattr_noperm+0x22f/0xb00 fs/xattr.c:234
 __vfs_setxattr_locked+0x441/0x480 fs/xattr.c:295
 vfs_setxattr+0x294/0x650 fs/xattr.c:321
 do_setxattr fs/xattr.c:629 [inline]
 __do_sys_fsetxattr fs/xattr.c:710 [inline]
 __se_sys_fsetxattr+0x7f0/0x980 fs/xattr.c:686
 __x64_sys_fsetxattr+0xe4/0x150 fs/xattr.c:686
 x64_sys_call+0x19c3/0x3ba0 arch/x86/include/generated/asm/syscalls_64.h:191
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Uninit was stored to memory at:
 ea_put fs/jfs/xattr.c:639 [inline]
 __jfs_setxattr+0x185f/0x1ae0 fs/jfs/xattr.c:785
 __jfs_xattr_set+0xe6/0x1f0 fs/jfs/xattr.c:934
 jfs_xattr_set+0x79/0x90 fs/jfs/xattr.c:958
 __vfs_setxattr+0x844/0x8b0 fs/xattr.c:200
 __vfs_setxattr_noperm+0x22f/0xb00 fs/xattr.c:234
 __vfs_setxattr_locked+0x441/0x480 fs/xattr.c:295
 vfs_setxattr+0x294/0x650 fs/xattr.c:321
 do_setxattr fs/xattr.c:629 [inline]
 __do_sys_fsetxattr fs/xattr.c:710 [inline]
 __se_sys_fsetxattr+0x7f0/0x980 fs/xattr.c:686
 __x64_sys_fsetxattr+0xe4/0x150 fs/xattr.c:686
 x64_sys_call+0x19c3/0x3ba0 arch/x86/include/generated/asm/syscalls_64.h:191
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Local variable ea_buf created at:
 __jfs_setxattr+0x5d/0x1ae0 fs/jfs/xattr.c:662
 __jfs_xattr_set+0xe6/0x1f0 fs/jfs/xattr.c:934

CPU: 0 UID: 0 PID: 81 Comm: kswapd0 Tainted: G        W          6.11.0-rc5-syzkaller #0
Tainted: [W]=WARN
=====================================================

The reason is ea_buf->new_ea is not initialized properly.

Fix this by using memset to empty its content at the beginning
in ea_get().

Reported-by: syzbot+02341e0daa42a15ce130@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=02341e0daa42a15ce130
Signed-off-by: Zhao Mengmeng <zhaomengmeng@xxxxxxxxxx>
---
 fs/jfs/xattr.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/jfs/xattr.c b/fs/jfs/xattr.c
index 2999ed5d83f5..0fb05e314edf 100644
--- a/fs/jfs/xattr.c
+++ b/fs/jfs/xattr.c
@@ -434,6 +434,8 @@ static int ea_get(struct inode *inode, struct ea_buffer *ea_buf, int min_size)
 	int rc;
 	int quota_allocation = 0;
 
+	memset(&ea_buf->new_ea, 0, sizeof(ea_buf->new_ea));
+
 	/* When fsck.jfs clears a bad ea, it doesn't clear the size */
 	if (ji->ea.flag == 0)
 		ea_size = 0;
-- 
2.43.0