[PATCH] gfs2: Fix error pointer dereference

[PATCH] gfs2: Fix error pointer dereference

[Ethan Tidmore]

The function __filemap_get_folio() can return an error pointer and is
not checked for one. Add check for error pointer.

Detected by Smatch:
fs/gfs2/meta_io.c:147 gfs2_getbuf() error:
'folio' dereferencing possible ERR_PTR()

Fixes: 0eb751791df86 ("gfs2: convert gfs2_getbuf() to folios")
Signed-off-by: Ethan Tidmore <ethantidmore06@gmail.com>
---
 fs/gfs2/meta_io.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/gfs2/meta_io.c b/fs/gfs2/meta_io.c
index 3c8e4553102d..9c0ba4c3cb29 100644
--- a/fs/gfs2/meta_io.c
+++ b/fs/gfs2/meta_io.c
@@ -144,6 +144,8 @@ struct buffer_head *gfs2_getbuf(struct gfs2_glock *gl, u64 blkno, int create)
 		folio = __filemap_get_folio(mapping, index,
 				FGP_LOCK | FGP_ACCESSED | FGP_CREAT,
 				mapping_gfp_mask(mapping) | __GFP_NOFAIL);
+		if (IS_ERR(folio))
+			return NULL;
 		bh = folio_buffers(folio);
 		if (!bh)
 			bh = create_empty_buffers(folio,
-- 
2.53.0

Re: [PATCH] gfs2: Fix error pointer dereference

[Matthew Wilcox]

On Wed, Feb 18, 2026 at 02:06:45PM -0600, Ethan Tidmore wrote:
> The function __filemap_get_folio() can return an error pointer and is
> not checked for one. Add check for error pointer.

Can you explain how __filemap_get_folio() would fail, given the
presence of __GFP_NOFAIL in the GFP flags?

> Detected by Smatch:
> fs/gfs2/meta_io.c:147 gfs2_getbuf() error:
> 'folio' dereferencing possible ERR_PTR()
> 
> Fixes: 0eb751791df86 ("gfs2: convert gfs2_getbuf() to folios")
> Signed-off-by: Ethan Tidmore <ethantidmore06@gmail.com>
> ---
>  fs/gfs2/meta_io.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/fs/gfs2/meta_io.c b/fs/gfs2/meta_io.c
> index 3c8e4553102d..9c0ba4c3cb29 100644
> --- a/fs/gfs2/meta_io.c
> +++ b/fs/gfs2/meta_io.c
> @@ -144,6 +144,8 @@ struct buffer_head *gfs2_getbuf(struct gfs2_glock *gl, u64 blkno, int create)
>  		folio = __filemap_get_folio(mapping, index,
>  				FGP_LOCK | FGP_ACCESSED | FGP_CREAT,
>  				mapping_gfp_mask(mapping) | __GFP_NOFAIL);
> +		if (IS_ERR(folio))
> +			return NULL;
>  		bh = folio_buffers(folio);
>  		if (!bh)
>  			bh = create_empty_buffers(folio,
> -- 
> 2.53.0
> 

Re: [PATCH] gfs2: Fix error pointer dereference

[Ethan Tidmore]

On Wed Feb 18, 2026 at 3:14 PM CST, Matthew Wilcox wrote:
> On Wed, Feb 18, 2026 at 02:06:45PM -0600, Ethan Tidmore wrote:
>> The function __filemap_get_folio() can return an error pointer and is
>> not checked for one. Add check for error pointer.
>
> Can you explain how __filemap_get_folio() would fail, given the
> presence of __GFP_NOFAIL in the GFP flags?
>

I hadn't thought of that, looks like Smatch gave me a false positive. I
just saw the same function being called a few lines down and its return
value being checked for error pointer so I just assumed this one was
missing. Sorry about that.

Thanks,

ET