linux-ext4 - [PATCH] ext4: fix error pointer dereference in ext4_mb_load_buddy

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Message-ID: <eaafa1d9-a61c-4af4-9f97-d3ad72c60200@moroto.mountain>
Date: Fri, 10 May 2024 18:22:53 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Matthew Wilcox <willy@...radead.org>
Cc: Theodore Ts'o <tytso@....edu>,
	Andreas Dilger <adilger.kernel@...ger.ca>,
	linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: [PATCH] ext4: fix error pointer dereference in
 ext4_mb_load_buddy_gfp()

This code calls folio_put() on an error pointer which will lead to a
crash.  Check for both error pointers and NULL pointers before calling
folio_put().

Fixes: 5eea586b47f0 ("ext4: convert bd_buddy_page to bd_buddy_folio")
Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
---
 fs/ext4/mballoc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 648989c125f2..9dda9cd68ab2 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -1717,7 +1717,7 @@ ext4_mb_load_buddy_gfp(struct super_block *sb, ext4_group_t group,
 	return 0;
 
 err:
-	if (folio)
+	if (!IS_ERR_OR_NULL(folio))
 		folio_put(folio);
 	if (e4b->bd_bitmap_folio)
 		folio_put(e4b->bd_bitmap_folio);
-- 
2.43.0