From: Darrick J. Wong <djwong@xxxxxxxxxx>
generic/361 popped up this weird error:
generic/361 [failed, exit status 1]- output mismatch (see /var/tmp/fstests/generic/361.out.bad)
--- tests/generic/361.out 2025-04-30 16:20:44.563589363 -0700
+++ /var/tmp/fstests/generic/361.out.bad 2025-06-11 10:40:07.475036412 -0700
@@ -1,2 +1,2 @@
QA output created by 361
-Silence is golden
+mkfs.fuse.ext4: Input/output error while writing out and closing file system
...
(Run 'diff -u /run/fstests/bin/tests/generic/361.out /var/tmp/fstests/generic/361.out.bad' to see the entire diff)
The test formats a small filesystem, creates a larger sparse file, loop
mounts it, and tries to format an ext4 filesystem on the loopdev. The
loop driver sends fallocate zero_range requests to fuse2fs, but stumbles
over this extent tree layout when fallocating 16 blocks at offset 145:
EXTENTS:
(262128-262143[u]):2127-2142
fallocate goes to offset 145, and sees the right-extent at 262128.
Oddly, it then tries to allocate 262128-145 blocks instead of the 16
that were asked for, so it tries to allocate a huge number of blocks
but then crashes and burns when it runs out of space.
Fix this by constraining the len parameter to ext_falloc_helper to the
correct value.
Cc: <linux-ext4@xxxxxxxxxxxxxxx> # v1.43
Fixes: 5aad5b8e0e3cfa ("libext2fs: implement fallocate")
Signed-off-by: "Darrick J. Wong" <djwong@xxxxxxxxxx>
---
lib/ext2fs/fallocate.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/lib/ext2fs/fallocate.c b/lib/ext2fs/fallocate.c
index 063242c5fa4e6b..1ef989cd38214d 100644
--- a/lib/ext2fs/fallocate.c
+++ b/lib/ext2fs/fallocate.c
@@ -718,7 +718,8 @@ static errcode_t extent_fallocate(ext2_filsys fs, int flags, ext2_ino_t ino,
goal = left_extent.e_pblk - (left_extent.e_lblk - start);
err = ext_falloc_helper(fs, flags, ino, inode, handle, NULL,
&left_extent, start,
- left_extent.e_lblk - start, goal);
+ min(len, left_extent.e_lblk - start),
+ goal);
if (err)
goto errout;
