[U-Boot] [PATCH] ext4: fix possible crash on directory traversal, ignore deleted entries

[Tom Rini]

On Sun, Aug 14, 2016 at 05:11:04AM +0200, Stefan Brüns wrote:

> The following command triggers a segfault in search_dir:
> ./sandbox/u-boot -c 'host bind 0 ./sandbox/test/fs/3GB.ext4.img ;
>     ext4write host 0 0 /./foo 0x10'
> 
> The following command triggers a segfault in check_filename:
> ./sandbox/u-boot -c 'host bind 0 ./sandbox/test/fs/3GB.ext4.img ;
>     ext4write host 0 0 /. 0x10'
> 
> "." is the first entry in the directory, thus previous_dir is NULL. The
> whole previous_dir block in search_dir seems to be a bad copy from
> check_filename(...). As the changed data is not written to disk, the
> statement is mostly harmless, save the possible NULL-ptr reference.
> 
> Typically a file is unlinked by extending the direntlen of the previous
> entry. If the entry is the first entry in the directory block, it is
> invalidated by setting inode=0.
> 
> The inode==0 case is hard to trigger without crafted filesystems. It only
> hits if the first entry in a directory block is deleted and later a lookup
> for the entry (by name) is done.
> 
> Signed-off-by: Stefan Brüns <stefan.bruens at rwth-aachen.de>
> ---
>  fs/ext4/ext4_common.c | 57 ++++++++++++++++++---------------------------------
>  fs/ext4/ext4_write.c  |  2 +-
>  include/ext4fs.h      |  2 +-
>  3 files changed, 22 insertions(+), 39 deletions(-)

Can you please add the test case to the existing scripts?  Thanks!

-- 
Tom
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