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Subject[PATCH] ocfs2: fix the oops problem when write cloned file
Date
Writing a cloned file triggers a kernel oops and the user-space
command process is also killed by the system.
The bug can be reproduced stably, e.g.
1)create a file under ocfs2 file system directory.
journalctl -b > aa.txt
2)create a cloned file for this file.
reflink aa.txt bb.txt
3)write the cloned file with dd command.
dd if=/dev/zero of=bb.txt bs=512 count=1 conv=notrunc

The dd command is killed by the kernel, then you can see the oops
message via dmesg command.

[ 463.875404] BUG: kernel NULL pointer dereference, address: 0000000000000028
[ 463.875413] #PF: supervisor read access in kernel mode
[ 463.875416] #PF: error_code(0x0000) - not-present page
[ 463.875418] PGD 0 P4D 0
[ 463.875425] Oops: 0000 [#1] SMP PTI
[ 463.875431] CPU: 1 PID: 2291 Comm: dd Tainted: G OE 5.3.16-2-default
[ 463.875433] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
[ 463.875500] RIP: 0010:ocfs2_refcount_cow+0xa4/0x5d0 [ocfs2]
[ 463.875505] Code: 06 89 6c 24 38 89 eb f6 44 24 3c 02 74 be 49 8b 47 28
[ 463.875508] RSP: 0018:ffffa2cb409dfce8 EFLAGS: 00010202
[ 463.875512] RAX: ffff8b1ebdca8000 RBX: 0000000000000001 RCX: ffff8b1eb73a9df0
[ 463.875515] RDX: 0000000000056a01 RSI: 0000000000000000 RDI: 0000000000000000
[ 463.875517] RBP: 0000000000000001 R08: ffff8b1eb73a9de0 R09: 0000000000000000
[ 463.875520] R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000
[ 463.875522] R13: ffff8b1eb922f048 R14: 0000000000000000 R15: ffff8b1eb922f048
[ 463.875526] FS: 00007f8f44d15540(0000) GS:ffff8b1ebeb00000(0000) knlGS:0000000000000000
[ 463.875529] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 463.875532] CR2: 0000000000000028 CR3: 000000003c17a000 CR4: 00000000000006e0
[ 463.875546] Call Trace:
[ 463.875596] ? ocfs2_inode_lock_full_nested+0x18b/0x960 [ocfs2]
[ 463.875648] ocfs2_file_write_iter+0xaf8/0xc70 [ocfs2]
[ 463.875672] new_sync_write+0x12d/0x1d0
[ 463.875688] vfs_write+0xad/0x1a0
[ 463.875697] ksys_write+0xa1/0xe0
[ 463.875710] do_syscall_64+0x60/0x1f0
[ 463.875743] entry_SYSCALL_64_after_hwframe+0x49/0xbe
[ 463.875758] RIP: 0033:0x7f8f4482ed44
[ 463.875762] Code: 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 80 00 00 00
[ 463.875765] RSP: 002b:00007fff300a79d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
[ 463.875769] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f8f4482ed44
[ 463.875771] RDX: 0000000000000200 RSI: 000055f771b5c000 RDI: 0000000000000001
[ 463.875774] RBP: 0000000000000200 R08: 00007f8f44af9c78 R09: 0000000000000003
[ 463.875776] R10: 000000000000089f R11: 0000000000000246 R12: 000055f771b5c000
[ 463.875779] R13: 0000000000000200 R14: 0000000000000000 R15: 000055f771b5c000

This regression problem was introduced by commit e74540b28556 ("ocfs2:
protect extent tree in ocfs2_prepare_inode_for_write()").

Fixes: e74540b28556 ("ocfs2: protect extent tree in ocfs2_prepare_inode_for_write()").
Signed-off-by: Gang He <ghe@suse.com>
---
fs/ocfs2/file.c | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index 9876db52913a..6cd5e4924e4d 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -2101,17 +2101,15 @@ static int ocfs2_is_io_unaligned(struct inode *inode, size_t count, loff_t pos)
static int ocfs2_inode_lock_for_extent_tree(struct inode *inode,
struct buffer_head **di_bh,
int meta_level,
- int overwrite_io,
int write_sem,
int wait)
{
int ret = 0;

if (wait)
- ret = ocfs2_inode_lock(inode, NULL, meta_level);
+ ret = ocfs2_inode_lock(inode, di_bh, meta_level);
else
- ret = ocfs2_try_inode_lock(inode,
- overwrite_io ? NULL : di_bh, meta_level);
+ ret = ocfs2_try_inode_lock(inode, di_bh, meta_level);
if (ret < 0)
goto out;

@@ -2136,6 +2134,7 @@ static int ocfs2_inode_lock_for_extent_tree(struct inode *inode,

out_unlock:
brelse(*di_bh);
+ *di_bh = NULL;
ocfs2_inode_unlock(inode, meta_level);
out:
return ret;
@@ -2177,7 +2176,6 @@ static int ocfs2_prepare_inode_for_write(struct file *file,
ret = ocfs2_inode_lock_for_extent_tree(inode,
&di_bh,
meta_level,
- overwrite_io,
write_sem,
wait);
if (ret < 0) {
@@ -2233,13 +2231,13 @@ static int ocfs2_prepare_inode_for_write(struct file *file,
&di_bh,
meta_level,
write_sem);
+ meta_level = 1;
+ write_sem = 1;
ret = ocfs2_inode_lock_for_extent_tree(inode,
&di_bh,
meta_level,
- overwrite_io,
- 1,
+ write_sem,
wait);
- write_sem = 1;
if (ret < 0) {
if (ret != -EAGAIN)
mlog_errno(ret);
--
2.12.3
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