linux-ext4 - [PATCH AUTOSEL 5.15 40/47] ext2: Use kvmalloc() for group descriptor array

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Date:   Wed, 12 Oct 2022 20:21:15 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Jan Kara <jack@...e.cz>,
        syzbot+0f2f7e65a3007d39539f@...kaller.appspotmail.com,
        Sasha Levin <sashal@...nel.org>, jack@...e.com,
        linux-ext4@...r.kernel.org
Subject: [PATCH AUTOSEL 5.15 40/47] ext2: Use kvmalloc() for group descriptor array

From: Jan Kara <jack@...e.cz>

[ Upstream commit e7c7fbb9a8574ebd89cc05db49d806c7476863ad ]

Array of group descriptor block buffers can get rather large. In theory
in can reach 1MB for perfectly valid filesystem and even more for
maliciously crafted ones. Use kvmalloc() to allocate the array to avoid
straining memory allocator with large order allocations unnecessarily.

Reported-by: syzbot+0f2f7e65a3007d39539f@...kaller.appspotmail.com
Signed-off-by: Jan Kara <jack@...e.cz>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/ext2/super.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/ext2/super.c b/fs/ext2/super.c
index fd855574ef09..02d82f8fe85d 100644
--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -163,7 +163,7 @@ static void ext2_put_super (struct super_block * sb)
 	db_count = sbi->s_gdb_count;
 	for (i = 0; i < db_count; i++)
 		brelse(sbi->s_group_desc[i]);
-	kfree(sbi->s_group_desc);
+	kvfree(sbi->s_group_desc);
 	kfree(sbi->s_debts);
 	percpu_counter_destroy(&sbi->s_freeblocks_counter);
 	percpu_counter_destroy(&sbi->s_freeinodes_counter);
@@ -1080,7 +1080,7 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent)
 	}
 	db_count = (sbi->s_groups_count + EXT2_DESC_PER_BLOCK(sb) - 1) /
 		   EXT2_DESC_PER_BLOCK(sb);
-	sbi->s_group_desc = kmalloc_array(db_count,
+	sbi->s_group_desc = kvmalloc_array(db_count,
 					   sizeof(struct buffer_head *),
 					   GFP_KERNEL);
 	if (sbi->s_group_desc == NULL) {
@@ -1206,7 +1206,7 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent)
 	for (i = 0; i < db_count; i++)
 		brelse(sbi->s_group_desc[i]);
 failed_mount_group_desc:
-	kfree(sbi->s_group_desc);
+	kvfree(sbi->s_group_desc);
 	kfree(sbi->s_debts);
 failed_mount:
 	brelse(bh);
-- 
2.35.1