fs/ext4/super.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
I caught a null-ptr-deref bug as follows:
==================================================================
KASAN: null-ptr-deref in range [0x0000000000000068-0x000000000000006f]
CPU: 1 PID: 1589 Comm: umount Not tainted 5.10.0-02219-dirty #339
RIP: 0010:ext4_write_info+0x53/0x1b0
[...]
Call Trace:
dquot_writeback_dquots+0x341/0x9a0
ext4_sync_fs+0x19e/0x800
__sync_filesystem+0x83/0x100
sync_filesystem+0x89/0xf0
generic_shutdown_super+0x79/0x3e0
kill_block_super+0xa1/0x110
deactivate_locked_super+0xac/0x130
deactivate_super+0xb6/0xd0
cleanup_mnt+0x289/0x400
__cleanup_mnt+0x16/0x20
task_work_run+0x11c/0x1c0
exit_to_user_mode_prepare+0x203/0x210
syscall_exit_to_user_mode+0x5b/0x3a0
do_syscall_64+0x59/0x70
entry_SYSCALL_64_after_hwframe+0x44/0xa9
==================================================================
Above issue may happen as follows:
-------------------------------------
exit_to_user_mode_prepare
task_work_run
__cleanup_mnt
cleanup_mnt
deactivate_super
deactivate_locked_super
kill_block_super
generic_shutdown_super
shrink_dcache_for_umount
dentry = sb->s_root
sb->s_root = NULL <--- Here set NULL
sync_filesystem
__sync_filesystem
sb->s_op->sync_fs > ext4_sync_fs
dquot_writeback_dquots
sb->dq_op->write_info > ext4_write_info
ext4_journal_start(d_inode(sb->s_root), EXT4_HT_QUOTA, 2)
d_inode(sb->s_root)
s_root->d_inode <--- Null pointer dereference
To solve this problem, we use ext4_journal_start_sb directly
to avoid s_root being used.
Signed-off-by: Baokun Li <libaokun1@huawei.com>
---
fs/ext4/super.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 9a66abcca1a8..0ce4565422f6 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -6653,7 +6653,7 @@ static int ext4_write_info(struct super_block *sb, int type)
handle_t *handle;
/* Data block + inode block */
- handle = ext4_journal_start(d_inode(sb->s_root), EXT4_HT_QUOTA, 2);
+ handle = ext4_journal_start_sb(sb, EXT4_HT_QUOTA, 2);
if (IS_ERR(handle))
return PTR_ERR(handle);
ret = dquot_commit_info(sb, type);
--
2.31.1On Fri, 5 Aug 2022 20:39:47 +0800, Baokun Li wrote:
> I caught a null-ptr-deref bug as follows:
> ==================================================================
> KASAN: null-ptr-deref in range [0x0000000000000068-0x000000000000006f]
> CPU: 1 PID: 1589 Comm: umount Not tainted 5.10.0-02219-dirty #339
> RIP: 0010:ext4_write_info+0x53/0x1b0
> [...]
> Call Trace:
> dquot_writeback_dquots+0x341/0x9a0
> ext4_sync_fs+0x19e/0x800
> __sync_filesystem+0x83/0x100
> sync_filesystem+0x89/0xf0
> generic_shutdown_super+0x79/0x3e0
> kill_block_super+0xa1/0x110
> deactivate_locked_super+0xac/0x130
> deactivate_super+0xb6/0xd0
> cleanup_mnt+0x289/0x400
> __cleanup_mnt+0x16/0x20
> task_work_run+0x11c/0x1c0
> exit_to_user_mode_prepare+0x203/0x210
> syscall_exit_to_user_mode+0x5b/0x3a0
> do_syscall_64+0x59/0x70
> entry_SYSCALL_64_after_hwframe+0x44/0xa9
> ==================================================================
>
> [...]
Applied, thanks!
[1/1] ext4: fix null-ptr-deref in ext4_write_info
commit: 647642bf8f326994d7eaf785bba3fa9dad92cff0
Best regards,
--
Theodore Ts'o <tytso@mit.edu>
On Fri, Aug 05, 2022 at 08:39:47PM +0800, Baokun Li wrote: > I caught a null-ptr-deref bug as follows: > ================================================================== > KASAN: null-ptr-deref in range [0x0000000000000068-0x000000000000006f] > CPU: 1 PID: 1589 Comm: umount Not tainted 5.10.0-02219-dirty #339 > RIP: 0010:ext4_write_info+0x53/0x1b0 > [...] > Call Trace: > dquot_writeback_dquots+0x341/0x9a0 > ext4_sync_fs+0x19e/0x800 > __sync_filesystem+0x83/0x100 > sync_filesystem+0x89/0xf0 > generic_shutdown_super+0x79/0x3e0 > kill_block_super+0xa1/0x110 > deactivate_locked_super+0xac/0x130 > deactivate_super+0xb6/0xd0 > cleanup_mnt+0x289/0x400 > __cleanup_mnt+0x16/0x20 > task_work_run+0x11c/0x1c0 > exit_to_user_mode_prepare+0x203/0x210 > syscall_exit_to_user_mode+0x5b/0x3a0 > do_syscall_64+0x59/0x70 > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > ================================================================== > > Above issue may happen as follows: > ------------------------------------- > exit_to_user_mode_prepare > task_work_run > __cleanup_mnt > cleanup_mnt > deactivate_super > deactivate_locked_super > kill_block_super > generic_shutdown_super > shrink_dcache_for_umount > dentry = sb->s_root > sb->s_root = NULL <--- Here set NULL > sync_filesystem > __sync_filesystem > sb->s_op->sync_fs > ext4_sync_fs > dquot_writeback_dquots > sb->dq_op->write_info > ext4_write_info > ext4_journal_start(d_inode(sb->s_root), EXT4_HT_QUOTA, 2) > d_inode(sb->s_root) > s_root->d_inode <--- Null pointer dereference > > To solve this problem, we use ext4_journal_start_sb directly > to avoid s_root being used. Are we syncing the file system after the superblock shutdown and getting away with it? This does not look good. Do you have a reproducer? Thanks! -Lukas > > Signed-off-by: Baokun Li <libaokun1@huawei.com> > --- > fs/ext4/super.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/ext4/super.c b/fs/ext4/super.c > index 9a66abcca1a8..0ce4565422f6 100644 > --- a/fs/ext4/super.c > +++ b/fs/ext4/super.c > @@ -6653,7 +6653,7 @@ static int ext4_write_info(struct super_block *sb, int type) > handle_t *handle; > > /* Data block + inode block */ > - handle = ext4_journal_start(d_inode(sb->s_root), EXT4_HT_QUOTA, 2); > + handle = ext4_journal_start_sb(sb, EXT4_HT_QUOTA, 2); > if (IS_ERR(handle)) > return PTR_ERR(handle); > ret = dquot_commit_info(sb, type); > -- > 2.31.1 >
在 2022/8/5 21:07, Lukas Czerner 写道: > On Fri, Aug 05, 2022 at 08:39:47PM +0800, Baokun Li wrote: >> I caught a null-ptr-deref bug as follows: >> ================================================================== >> KASAN: null-ptr-deref in range [0x0000000000000068-0x000000000000006f] >> CPU: 1 PID: 1589 Comm: umount Not tainted 5.10.0-02219-dirty #339 >> RIP: 0010:ext4_write_info+0x53/0x1b0 >> [...] >> Call Trace: >> dquot_writeback_dquots+0x341/0x9a0 >> ext4_sync_fs+0x19e/0x800 >> __sync_filesystem+0x83/0x100 >> sync_filesystem+0x89/0xf0 >> generic_shutdown_super+0x79/0x3e0 >> kill_block_super+0xa1/0x110 >> deactivate_locked_super+0xac/0x130 >> deactivate_super+0xb6/0xd0 >> cleanup_mnt+0x289/0x400 >> __cleanup_mnt+0x16/0x20 >> task_work_run+0x11c/0x1c0 >> exit_to_user_mode_prepare+0x203/0x210 >> syscall_exit_to_user_mode+0x5b/0x3a0 >> do_syscall_64+0x59/0x70 >> entry_SYSCALL_64_after_hwframe+0x44/0xa9 >> ================================================================== >> >> Above issue may happen as follows: >> ------------------------------------- >> exit_to_user_mode_prepare >> task_work_run >> __cleanup_mnt >> cleanup_mnt >> deactivate_super >> deactivate_locked_super >> kill_block_super >> generic_shutdown_super >> shrink_dcache_for_umount >> dentry = sb->s_root >> sb->s_root = NULL <--- Here set NULL >> sync_filesystem >> __sync_filesystem >> sb->s_op->sync_fs > ext4_sync_fs >> dquot_writeback_dquots >> sb->dq_op->write_info > ext4_write_info >> ext4_journal_start(d_inode(sb->s_root), EXT4_HT_QUOTA, 2) >> d_inode(sb->s_root) >> s_root->d_inode <--- Null pointer dereference >> >> To solve this problem, we use ext4_journal_start_sb directly >> to avoid s_root being used. > Are we syncing the file system after the superblock shutdown and getting > away with it? This does not look good. Do you have a reproducer? > > Thanks! > -Lukas Hi, Lukas! This problem is triggered by a pressure test when I reproduce another problem. So I didn't have the reproducer. I looked at the error stack code and found that it seems there is something wrong. Moreover, it's really weird to write code like "ext4_journal_start(d_inode(sb->s_root), ...)". >> Signed-off-by: Baokun Li <libaokun1@huawei.com> >> --- >> fs/ext4/super.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/fs/ext4/super.c b/fs/ext4/super.c >> index 9a66abcca1a8..0ce4565422f6 100644 >> --- a/fs/ext4/super.c >> +++ b/fs/ext4/super.c >> @@ -6653,7 +6653,7 @@ static int ext4_write_info(struct super_block *sb, int type) >> handle_t *handle; >> >> /* Data block + inode block */ >> - handle = ext4_journal_start(d_inode(sb->s_root), EXT4_HT_QUOTA, 2); >> + handle = ext4_journal_start_sb(sb, EXT4_HT_QUOTA, 2); >> if (IS_ERR(handle)) >> return PTR_ERR(handle); >> ret = dquot_commit_info(sb, type); >> -- >> 2.31.1 >> > . Thanks! -- With Best Regards, Baokun Li
On Wed 10-08-22 15:20:48, Baokun Li wrote: > 在 2022/8/5 21:07, Lukas Czerner 写道: > > On Fri, Aug 05, 2022 at 08:39:47PM +0800, Baokun Li wrote: > > > I caught a null-ptr-deref bug as follows: > > > ================================================================== > > > KASAN: null-ptr-deref in range [0x0000000000000068-0x000000000000006f] > > > CPU: 1 PID: 1589 Comm: umount Not tainted 5.10.0-02219-dirty #339 > > > RIP: 0010:ext4_write_info+0x53/0x1b0 > > > [...] > > > Call Trace: > > > dquot_writeback_dquots+0x341/0x9a0 > > > ext4_sync_fs+0x19e/0x800 > > > __sync_filesystem+0x83/0x100 > > > sync_filesystem+0x89/0xf0 > > > generic_shutdown_super+0x79/0x3e0 > > > kill_block_super+0xa1/0x110 > > > deactivate_locked_super+0xac/0x130 > > > deactivate_super+0xb6/0xd0 > > > cleanup_mnt+0x289/0x400 > > > __cleanup_mnt+0x16/0x20 > > > task_work_run+0x11c/0x1c0 > > > exit_to_user_mode_prepare+0x203/0x210 > > > syscall_exit_to_user_mode+0x5b/0x3a0 > > > do_syscall_64+0x59/0x70 > > > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > > ================================================================== > > > > > > Above issue may happen as follows: > > > ------------------------------------- > > > exit_to_user_mode_prepare > > > task_work_run > > > __cleanup_mnt > > > cleanup_mnt > > > deactivate_super > > > deactivate_locked_super > > > kill_block_super > > > generic_shutdown_super > > > shrink_dcache_for_umount > > > dentry = sb->s_root > > > sb->s_root = NULL <--- Here set NULL > > > sync_filesystem > > > __sync_filesystem > > > sb->s_op->sync_fs > ext4_sync_fs > > > dquot_writeback_dquots > > > sb->dq_op->write_info > ext4_write_info > > > ext4_journal_start(d_inode(sb->s_root), EXT4_HT_QUOTA, 2) > > > d_inode(sb->s_root) > > > s_root->d_inode <--- Null pointer dereference > > > > > > To solve this problem, we use ext4_journal_start_sb directly > > > to avoid s_root being used. > > Are we syncing the file system after the superblock shutdown and getting > > away with it? This does not look good. Do you have a reproducer? > > > > Thanks! > > -Lukas > > Hi, Lukas! > > This problem is triggered by a pressure test when I reproduce another > problem. > > So I didn't have the reproducer. > > I looked at the error stack code and found that it seems there is something > wrong. > > Moreover, it's really weird to write code like > "ext4_journal_start(d_inode(sb->s_root), ...)". I agree. That looks like some leftover from the past. Feel free to add: Reviewed-by: Jan Kara <jack@suse.cz> Honza > > > > Signed-off-by: Baokun Li <libaokun1@huawei.com> > > > --- > > > fs/ext4/super.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/fs/ext4/super.c b/fs/ext4/super.c > > > index 9a66abcca1a8..0ce4565422f6 100644 > > > --- a/fs/ext4/super.c > > > +++ b/fs/ext4/super.c > > > @@ -6653,7 +6653,7 @@ static int ext4_write_info(struct super_block *sb, int type) > > > handle_t *handle; > > > /* Data block + inode block */ > > > - handle = ext4_journal_start(d_inode(sb->s_root), EXT4_HT_QUOTA, 2); > > > + handle = ext4_journal_start_sb(sb, EXT4_HT_QUOTA, 2); > > > if (IS_ERR(handle)) > > > return PTR_ERR(handle); > > > ret = dquot_commit_info(sb, type); > > > -- > > > 2.31.1 > > > > > . > > > Thanks! > > -- > With Best Regards, > Baokun Li > -- Jan Kara <jack@suse.com> SUSE Labs, CR
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