diff mbox series

[1/2] dax: Check page->mapping isn't NULL

Message ID 20181127211634.4995-2-willy@infradead.org (mailing list archive)
State New, archived
Headers show
Series Two DAX fixes for 4.20 | expand

Commit Message

Matthew Wilcox Nov. 27, 2018, 9:16 p.m. UTC 
If we race with inode destroy, it's possible for page->mapping to be
NULL before we even enter this routine, as well as after having slept
waiting for the dax entry to become unlocked.

Fixes: c2a7d2a11552 ("filesystem-dax: Introduce dax_lock_mapping_entry()")
Cc: stable@vger.kernel.org
Reported-by: Jan Kara <jack@suse.cz>
Signed-off-by: Matthew Wilcox <willy@infradead.org>
---
 fs/dax.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Johannes Thumshirn Nov. 28, 2018, 9:18 a.m. UTC | #1 
Looks good,
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Jan Kara Nov. 28, 2018, 11:46 a.m. UTC | #2 
On Tue 27-11-18 13:16:33, Matthew Wilcox wrote:
> If we race with inode destroy, it's possible for page->mapping to be
> NULL before we even enter this routine, as well as after having slept
> waiting for the dax entry to become unlocked.
> 
> Fixes: c2a7d2a11552 ("filesystem-dax: Introduce dax_lock_mapping_entry()")
> Cc: stable@vger.kernel.org
> Reported-by: Jan Kara <jack@suse.cz>
> Signed-off-by: Matthew Wilcox <willy@infradead.org>

Thanks for writing this fix. The patch looks good. You can add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  fs/dax.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/dax.c b/fs/dax.c
> index 9bcce89ea18e..e69fc231833b 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -365,7 +365,7 @@ bool dax_lock_mapping_entry(struct page *page)
>  		struct address_space *mapping = READ_ONCE(page->mapping);
>  
>  		locked = false;
> -		if (!dax_mapping(mapping))
> +		if (!mapping || !dax_mapping(mapping))
>  			break;
>  
>  		/*
> -- 
> 2.19.1
>
diff mbox series

Patch

diff --git a/fs/dax.c b/fs/dax.c
index 9bcce89ea18e..e69fc231833b 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -365,7 +365,7 @@  bool dax_lock_mapping_entry(struct page *page)
 		struct address_space *mapping = READ_ONCE(page->mapping);
 
 		locked = false;
-		if (!dax_mapping(mapping))
+		if (!mapping || !dax_mapping(mapping))
 			break;
 
 		/*