Thanks for catching this, I added your fix to the ext4 patch queue http://repo.or.cz/w/ext4-patch-queue.git On Thu, 2008-01-10 at 17:31 +0300, Dmitry Monakhov wrote: > Hi, > While playing with new fancy fallocate interface on ext4 i've triggered > bug which corrupted my grub :). > > My testcase: > ~~~~~~~~~~~~ > blksize = 0x1000; > fd = open(argv[1], O_RDWR|O_CREAT, 0700); > unsigned long long sz = 0x10000000UL; > /* allocating big blocks chunk */ > syscall(__NR_fallocate, fd, 0, 0UL, sz) > > /* grab all other available filesystem space */ > tfd = open("tmp", O_RDWR|O_CREAT|O_DIRECT, 0700); > while( write(tfd, buf, 4096) > 0); /* loop untill ENOSPC */ > fsync(fd); /* just in case */ > while (pos < sz) { > /* each seek+ write operation result in splits uninitialized extent > in three extents. Splitting may result in new extent allocation > which probably will fail because of ENOSPC*/ > > lseek(fd, blksize*2 -1, SEEK_CUR); > if ((ret = write(fd, 'a', 1)) != 1) > exit(1); > pos += blksize * 2; > } > > Buggy place: > ~~~~~~~~~~~~ > ext4_ext_get_blocks(..., bh_result,..) > { > err = 0; > allocated = 0; > .... > ret = ext4_ext_convert_to_initialized(...) > if (ret < 0) > << By occasion real error code was lost here. > goto out2 > .... > out2: > .... > return err? err: allocated; > << Wow.. exit with "0", and caller assumes what bh_result was properly filled > << and then will submit it for write. But in fact bh contains random data in > << ->b_bdev, ->b_blocknr fileds :). > } > > Signed-off-by: Dmitry Monakhov <dmonakhov@xxxxxxxxxx> > --- > fs/ext4/extents.c | 5 +++-- > 1 files changed, 3 insertions(+), 2 deletions(-) > > diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c > index 8528774..fc8e508 100644 > --- a/fs/ext4/extents.c > +++ b/fs/ext4/extents.c > @@ -2320,9 +2320,10 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode, > ret = ext4_ext_convert_to_initialized(handle, inode, > path, iblock, > max_blocks); > - if (ret <= 0) > + if (ret <= 0) { > + err = ret; > goto out2; > - else > + } else > allocated = ret; > goto outnew; > } - To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
