Grr, looks like I accidentally reused a 'git send-email' from shell history which had a '--in-reply-to' in it. Please ignore and sorry about that. I've just resent a new email. Cheers, -- Luís On Wed, Oct 12, 2022 at 02:13:30PM +0100, Luís Henriques wrote: > The rec_len field in the directory entry has to be a multiple of 4. A > corrupted filesystem image can be used to hit a BUG() in > ext4_rec_len_to_disk(), called from make_indexed_dir(). > > ------------[ cut here ]------------ > kernel BUG at fs/ext4/ext4.h:2413! > ... > RIP: 0010:make_indexed_dir+0x53f/0x5f0 > ... > Call Trace: > <TASK> > ? add_dirent_to_buf+0x1b2/0x200 > ext4_add_entry+0x36e/0x480 > ext4_add_nondir+0x2b/0xc0 > ext4_create+0x163/0x200 > path_openat+0x635/0xe90 > do_filp_open+0xb4/0x160 > ? __create_object.isra.0+0x1de/0x3b0 > ? _raw_spin_unlock+0x12/0x30 > do_sys_openat2+0x91/0x150 > __x64_sys_open+0x6c/0xa0 > do_syscall_64+0x3c/0x80 > entry_SYSCALL_64_after_hwframe+0x46/0xb0 > > The fix simply adds a call to ext4_check_dir_entry() to validate the > directory entry, returning -EFSCORRUPTED if the entry is invalid. > > CC: stable@xxxxxxxxxxxxxxx > Link: https://bugzilla.kernel.org/show_bug.cgi?id=216540 > Signed-off-by: Luís Henriques <lhenriques@xxxxxxx> > --- > * Changes since v1: > > As suggested by Ted, I've removed the incorrect 'de->rec_len' check from > previous version and replaced it with a call to ext4_check_dir_entry() > instead, which is a much more complete verification. > > fs/ext4/namei.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c > index 3a31b662f661..ed76e89ffbe9 100644 > --- a/fs/ext4/namei.c > +++ b/fs/ext4/namei.c > @@ -2254,8 +2254,16 @@ static int make_indexed_dir(handle_t *handle, struct ext4_filename *fname, > memset(de, 0, len); /* wipe old data */ > de = (struct ext4_dir_entry_2 *) data2; > top = data2 + len; > - while ((char *)(de2 = ext4_next_entry(de, blocksize)) < top) > + while ((char *)(de2 = ext4_next_entry(de, blocksize)) < top) { > + if (ext4_check_dir_entry(dir, NULL, de, bh2, data2, len, > + (data2 + (blocksize - csum_size) - > + (char *) de))) { > + brelse(bh2); > + brelse(bh); > + return -EFSCORRUPTED; > + } > de = de2; > + } > de->rec_len = ext4_rec_len_to_disk(data2 + (blocksize - csum_size) - > (char *) de, blocksize); >
