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[PATCH] bfs: Fix sanity checks for empty files

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  [PATCH] bfs: Fix sanity checks for empty files Rakesh Pandit <rakesh@tuxera.com> - 2017-05-05 22:20 +0200
    Re: [PATCH] bfs: Fix sanity checks for empty files Tigran Aivazian <tigran@aivazian.fsnet.co.uk> - 2017-05-09 22:30 +0200

#1636711 — [PATCH] bfs: Fix sanity checks for empty files

Mount fails if file system image has empty files because of sanity
check while reading superblock. For empty files disk offset to end of
file (i_eoffset) is cpu_to_le32(-1). Sanity check comparison, which
compares disk offset with file system size isn't valid for this value
and hence is ignored with this patch.

Steps to reproduce:

$  dd if=/dev/zero of=bfs-image count=204800
$  mkfs.bfs bfs-image
$  mkdir bfs-mount-point
$  sudo mount -t bfs -o loop bfs-image bfs-mount-point/
$  cd bfs-mount-point/
$  sudo touch a
$  cd ..
$  sudo umount bfs-mount-point/
$  sudo mount -t bfs -o loop bfs-image bfs-mount-point/
mount: /dev/loop0: can't read superblock

$  dmesg
[25526.689580] BFS-fs: bfs_fill_super(): Inode 0x00000003 corrupted

Signed-off-by: Rakesh Pandit <rakesh@tuxera.com>
---

This was sent three years but maintainer has been unresponsive:
https://marc.info/?l=linux-kernel&m=138980764525250

So sending you Andrew as previous patches to bfs have gone through
your tree.  This is tested and reproducible.

 fs/bfs/inode.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/bfs/inode.c b/fs/bfs/inode.c
index f2deec0..0d3dc18 100644
--- a/fs/bfs/inode.c
+++ b/fs/bfs/inode.c
@@ -419,7 +419,7 @@ static int bfs_fill_super(struct super_block *s, void *data, int silent)
 		if (i_sblock > info->si_blocks ||
 			i_eblock > info->si_blocks ||
 			i_sblock > i_eblock ||
-			i_eoff > s_size ||
+			(i_eoff != le32_to_cpu(-1) && i_eoff > s_size) ||
 			i_sblock * BFS_BSIZE > i_eoff) {
 
 			printf("Inode 0x%08x corrupted\n", i);
-- 
2.9.3

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#1638392

Hi,

If you had created the filesystem with the proper mkfs under SCO
UnixWare 7 you (probably) wouldn't encounter this issue. But since
commercial Unix-es are now part of history and the only proper way is
the Linux mkfs.bfs utility, your patch is fine.

Kind regards,
Tigran

On 5 May 2017 at 21:16, Rakesh Pandit <rakesh@tuxera.com> wrote:
> Mount fails if file system image has empty files because of sanity
> check while reading superblock. For empty files disk offset to end of
> file (i_eoffset) is cpu_to_le32(-1). Sanity check comparison, which
> compares disk offset with file system size isn't valid for this value
> and hence is ignored with this patch.
>
> Steps to reproduce:
>
> $  dd if=/dev/zero of=bfs-image count=204800
> $  mkfs.bfs bfs-image
> $  mkdir bfs-mount-point
> $  sudo mount -t bfs -o loop bfs-image bfs-mount-point/
> $  cd bfs-mount-point/
> $  sudo touch a
> $  cd ..
> $  sudo umount bfs-mount-point/
> $  sudo mount -t bfs -o loop bfs-image bfs-mount-point/
> mount: /dev/loop0: can't read superblock
>
> $  dmesg
> [25526.689580] BFS-fs: bfs_fill_super(): Inode 0x00000003 corrupted
>
> Signed-off-by: Rakesh Pandit <rakesh@tuxera.com>
> ---
>
> This was sent three years but maintainer has been unresponsive:
> https://marc.info/?l=linux-kernel&m=138980764525250
>
> So sending you Andrew as previous patches to bfs have gone through
> your tree.  This is tested and reproducible.
>
>  fs/bfs/inode.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/bfs/inode.c b/fs/bfs/inode.c
> index f2deec0..0d3dc18 100644
> --- a/fs/bfs/inode.c
> +++ b/fs/bfs/inode.c
> @@ -419,7 +419,7 @@ static int bfs_fill_super(struct super_block *s, void *data, int silent)
>                 if (i_sblock > info->si_blocks ||
>                         i_eblock > info->si_blocks ||
>                         i_sblock > i_eblock ||
> -                       i_eoff > s_size ||
> +                       (i_eoff != le32_to_cpu(-1) && i_eoff > s_size) ||
>                         i_sblock * BFS_BSIZE > i_eoff) {
>
>                         printf("Inode 0x%08x corrupted\n", i);
> --
> 2.9.3
>

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