[PATCH] ext4: ext4_fill_super shouldn't return 0 on corruption

[PATCH] ext4: ext4_fill_super shouldn't return 0 on corruption

[Darrick J. Wong]

At the start of ext4_fill_super, ret is set to -EINVAL, and any failure path
out of that function returns this ret.  However, the generic_check_addressable
clause sets ret = 0 if it passes, which means that a subsequent failure (e.g.
a group checksum error) returns 0 even though the mount should fail.  This
causes vfs_kern_mount in turn to think that the mount succeeded (because
PTR_ERR(0) is false), leading to an oops.

A simple fix is to avoid using ret for the generic_check_addressable check,
which was last changed in commit 30ca22c70e3ef0a96ff84de69cd7e8561b416cb2.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
---

 fs/ext4/super.c |    5 ++---
 1 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 40131b7..a44bc59 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3257,9 +3257,8 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 	 * Test whether we have more sectors than will fit in sector_t,
 	 * and whether the max offset is addressable by the page cache.
 	 */
-	ret = generic_check_addressable(sb->s_blocksize_bits,
-					ext4_blocks_count(es));
-	if (ret) {
+	if (generic_check_addressable(sb->s_blocksize_bits,
+				      ext4_blocks_count(es))) {
 		ext4_msg(sb, KERN_ERR, "filesystem"
 			 " too large to mount safely on this system");
 		if (sizeof(sector_t) < 8)

Re: [PATCH] ext4: ext4_fill_super shouldn't return 0 on corruption

[Eric Sandeen]

On 11/15/10 3:48 PM, Darrick J. Wong wrote:
> At the start of ext4_fill_super, ret is set to -EINVAL, and any failure path
> out of that function returns this ret.  However, the generic_check_addressable
> clause sets ret = 0 if it passes, which means that a subsequent failure (e.g.
> a group checksum error) returns 0 even though the mount should fail.  This
> causes vfs_kern_mount in turn to think that the mount succeeded (because
> PTR_ERR(0) is false), leading to an oops.
> 
> A simple fix is to avoid using ret for the generic_check_addressable check,
> which was last changed in commit 30ca22c70e3ef0a96ff84de69cd7e8561b416cb2.
> 
> Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>

looks right, but one comment below:

> ---
> 
>  fs/ext4/super.c |    5 ++---
>  1 files changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 40131b7..a44bc59 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -3257,9 +3257,8 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
>  	 * Test whether we have more sectors than will fit in sector_t,
>  	 * and whether the max offset is addressable by the page cache.
>  	 */
> -	ret = generic_check_addressable(sb->s_blocksize_bits,
> -					ext4_blocks_count(es));
> -	if (ret) {
> +	if (generic_check_addressable(sb->s_blocksize_bits,
> +				      ext4_blocks_count(es))) {
>  		ext4_msg(sb, KERN_ERR, "filesystem"
>  			 " too large to mount safely on this system");
>  		if (sizeof(sector_t) < 8)

you probably want to set a "ret = -EFBIG" in here.

-Eric

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[PATCH] ext4: ext4_fill_super shouldn't return 0 on corruption

[Lukas Czerner]

At the start of ext4_fill_super, ret is set to -EINVAL, and any failure path
out of that function returns ret.  However, the generic_check_addressable
clause sets ret = 0 (if it passes), which means that a subsequent failure (e.g.
a group checksum error) returns 0 even though the mount should fail.  This
causes vfs_kern_mount in turn to think that the mount succeeded, leading to an
oops.

Signed-off-by: "Lukas Czerner" <lczerner@redhat.com>
Acked-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: Lukas Czerner <lczerner@redhat.com>
---
 fs/ext4/super.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 61182fe..3d89b72 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3268,13 +3268,14 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 	 * Test whether we have more sectors than will fit in sector_t,
 	 * and whether the max offset is addressable by the page cache.
 	 */
-	ret = generic_check_addressable(sb->s_blocksize_bits,
+	err = generic_check_addressable(sb->s_blocksize_bits,
 					ext4_blocks_count(es));
-	if (ret) {
+	if (err) {
 		ext4_msg(sb, KERN_ERR, "filesystem"
 			 " too large to mount safely on this system");
 		if (sizeof(sector_t) < 8)
 			ext4_msg(sb, KERN_WARNING, "CONFIG_LBDAF not enabled");
+		ret = err;
 		goto failed_mount;
 	}
 
-- 
1.7.2.3