Hi!
On 3/1/23 11:12, Jan Kara wrote:
Check that log of block size stored in the superblock has sensible
value. Otherwise the shift computing the block size can overflow leading
to undefined behavior.
Reported-by: syzbot+4fec412f59eba8c01b77@xxxxxxxxxxxxxxxxxxxxxxxxx
Would be helpful to also have:
LINK: https://syzkaller.appspot.com/bug?extid=4fec412f59eba8c01b77
a "Fixes:" tag and
Cc: stable@xxxxxxxxxxxxxxx
Cheers,
ta
Signed-off-by: Jan Kara <jack@xxxxxxx>
---
fs/ext2/ext2.h | 1 +
fs/ext2/super.c | 7 +++++++
2 files changed, 8 insertions(+)
diff --git a/fs/ext2/ext2.h b/fs/ext2/ext2.h
index 6c8e838bb278..8244366862e4 100644
--- a/fs/ext2/ext2.h
+++ b/fs/ext2/ext2.h
@@ -180,6 +180,7 @@ static inline struct ext2_sb_info *EXT2_SB(struct super_block *sb)
#define EXT2_MIN_BLOCK_SIZE 1024
#define EXT2_MAX_BLOCK_SIZE 65536
#define EXT2_MIN_BLOCK_LOG_SIZE 10
+#define EXT2_MAX_BLOCK_LOG_SIZE 16
#define EXT2_BLOCK_SIZE(s) ((s)->s_blocksize)
#define EXT2_ADDR_PER_BLOCK(s) (EXT2_BLOCK_SIZE(s) / sizeof (__u32))
#define EXT2_BLOCK_SIZE_BITS(s) ((s)->s_blocksize_bits)
diff --git a/fs/ext2/super.c b/fs/ext2/super.c
index 69c88facfe90..f342f347a695 100644
--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -945,6 +945,13 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent)
goto failed_mount;
}
+ if (le32_to_cpu(es->s_log_block_size) >
+ (EXT2_MAX_BLOCK_LOG_SIZE - BLOCK_SIZE_BITS)) {
+ ext2_msg(sb, KERN_ERR,
+ "Invalid log block size: %u",
+ le32_to_cpu(es->s_log_block_size));
+ goto failed_mount;
+ }
blocksize = BLOCK_SIZE << le32_to_cpu(sbi->s_es->s_log_block_size);
if (test_opt(sb, DAX)) {
