[PATCH] ext4: Detect already used quota file early

[PATCH] ext4: Detect already used quota file early

[Jan Kara]

When we try to use file already used as a quota file again (for the same
or different quota type), strange things can happen. At the very least
lockdep annotations may be wrong but also inode flags may be wrongly set
/ reset. When the file is used for two quota types at once we can even
corrupt the file and likely crash the kernel. Catch all these cases by
checking whether passed file is already used as quota file and bail
early in that case.

This fixes occasional generic/219 failure due to lockdep complaint.

Reported-by: Ritesh Harjani <riteshh@linux.ibm.com>
Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/ext4/super.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index ea425b49b345..49b2e6be35c4 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -6042,6 +6042,11 @@ static int ext4_quota_on(struct super_block *sb, int type, int format_id,
 	/* Quotafile not on the same filesystem? */
 	if (path->dentry->d_sb != sb)
 		return -EXDEV;
+
+	/* Quota already enabled for this file? */
+	if (path->dentry->d_inode->i_flags & S_NOQUOTA)
+		return -EBUSY;
+
 	/* Journaling quota? */
 	if (EXT4_SB(sb)->s_qf_names[type]) {
 		/* Quotafile not in fs root? */
-- 
2.16.4

Re: [PATCH] ext4: Detect already used quota file early

[Andreas Dilger]

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On Oct 13, 2020, at 7:22 AM, Jan Kara <jack@suse.cz> wrote:
> 
> When we try to use file already used as a quota file again (for the same
> or different quota type), strange things can happen. At the very least
> lockdep annotations may be wrong but also inode flags may be wrongly set
> / reset. When the file is used for two quota types at once we can even
> corrupt the file and likely crash the kernel. Catch all these cases by
> checking whether passed file is already used as quota file and bail
> early in that case.
> 
> This fixes occasional generic/219 failure due to lockdep complaint.
> 
> Reported-by: Ritesh Harjani <riteshh@linux.ibm.com>
> Signed-off-by: Jan Kara <jack@suse.cz>

Patch looks OK, but a minor question/suggestion below...

Reviewed-by: Andreas Dilger <adilger@dilger.ca>

> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index ea425b49b345..49b2e6be35c4 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -6042,6 +6042,11 @@ static int ext4_quota_on(struct super_block *sb, int type, int format_id,
> 	/* Quotafile not on the same filesystem? */
> 	if (path->dentry->d_sb != sb)
> 		return -EXDEV;
> +
> +	/* Quota already enabled for this file? */
> +	if (path->dentry->d_inode->i_flags & S_NOQUOTA)
> +		return -EBUSY;

Any reason not to use IS_NOQUOTA(path->dentry->d_inode) here?  I was trying
to see where S_NOQUOTA is set, and it seems that all of the quota code is
using IS_NOQUOTA().


Cheers, Andreas






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Re: [PATCH] ext4: Detect already used quota file early

[Jan Kara]

On Thu 15-10-20 01:33:24, Andreas Dilger wrote:
> On Oct 13, 2020, at 7:22 AM, Jan Kara <jack@suse.cz> wrote:
> > 
> > When we try to use file already used as a quota file again (for the same
> > or different quota type), strange things can happen. At the very least
> > lockdep annotations may be wrong but also inode flags may be wrongly set
> > / reset. When the file is used for two quota types at once we can even
> > corrupt the file and likely crash the kernel. Catch all these cases by
> > checking whether passed file is already used as quota file and bail
> > early in that case.
> > 
> > This fixes occasional generic/219 failure due to lockdep complaint.
> > 
> > Reported-by: Ritesh Harjani <riteshh@linux.ibm.com>
> > Signed-off-by: Jan Kara <jack@suse.cz>
> 
> Patch looks OK, but a minor question/suggestion below...
> 
> Reviewed-by: Andreas Dilger <adilger@dilger.ca>
> 
> > diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> > index ea425b49b345..49b2e6be35c4 100644
> > --- a/fs/ext4/super.c
> > +++ b/fs/ext4/super.c
> > @@ -6042,6 +6042,11 @@ static int ext4_quota_on(struct super_block *sb, int type, int format_id,
> > 	/* Quotafile not on the same filesystem? */
> > 	if (path->dentry->d_sb != sb)
> > 		return -EXDEV;
> > +
> > +	/* Quota already enabled for this file? */
> > +	if (path->dentry->d_inode->i_flags & S_NOQUOTA)
> > +		return -EBUSY;
> 
> Any reason not to use IS_NOQUOTA(path->dentry->d_inode) here?  I was trying
> to see where S_NOQUOTA is set, and it seems that all of the quota code is
> using IS_NOQUOTA().

OK, right. I'll change that. Thanks for review.

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

Re: [PATCH] ext4: Detect already used quota file early

[Theodore Y. Ts'o]

On Tue, Oct 13, 2020 at 03:22:21PM +0200, Jan Kara wrote:
> When we try to use file already used as a quota file again (for the same
> or different quota type), strange things can happen. At the very least
> lockdep annotations may be wrong but also inode flags may be wrongly set
> / reset. When the file is used for two quota types at once we can even
> corrupt the file and likely crash the kernel. Catch all these cases by
> checking whether passed file is already used as quota file and bail
> early in that case.
> 
> This fixes occasional generic/219 failure due to lockdep complaint.
> 
> Reported-by: Ritesh Harjani <riteshh@linux.ibm.com>
> Signed-off-by: Jan Kara <jack@suse.cz>

Thanks, applied.

					- Ted