[PATCH 5.8 017/148] squashfs: avoid bio_alloc() failure with 1Mbyte blocks

Greg Kroah-Hartman
2020-08-24T08:32:31Z

From: Phillip Lougher <phillip@squashfs.org.uk>

commit f26044c83e6e473a61917f5db411d1417327d425 upstream.

This is a regression introduced by the patch "migrate from ll_rw_block
usage to BIO".

Bio_alloc() is limited to 256 pages (1 Mbyte). This can cause a failure
when reading 1 Mbyte block filesystems. The problem is a datablock can be
fully (or almost uncompressed), requiring 256 pages, but, because blocks
are not aligned to page boundaries, it may require 257 pages to read.

Bio_kmalloc() can handle 1024 pages, and so use this for the edge
condition.

Fixes: 93e72b3c612a ("squashfs: migrate from ll_rw_block usage to BIO")
Reported-by: Nicolas Prochazka <nicolas.prochazka@gmail.com>
Reported-by: Tomoatsu Shimada <shimada@walbrix.com>
Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Cc: Philippe Liard <pliard@google.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Adrien Schildknecht <adrien+dev@schischi.me>
Cc: Daniel Rosenberg <drosen@google.com>
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/20200815035637.15319-1-phillip@squashfs.org.uk
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/squashfs/block.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

--- a/fs/squashfs/block.c
+++ b/fs/squashfs/block.c
@@ -87,7 +87,11 @@ static int squashfs_bio_read(struct supe
int error, i;
struct bio *bio;

- bio = bio_alloc(GFP_NOIO, page_count);
+ if (page_count <= BIO_MAX_PAGES)
+ bio = bio_alloc(GFP_NOIO, page_count);
+ else
+ bio = bio_kmalloc(GFP_NOIO, page_count);
+
if (!bio)
return -ENOMEM;