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.bru...@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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