linux-kernel - [PATCH 5.8 017/148] squashfs: avoid bio

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Message-Id: <20200824082414.791473408@linuxfoundation.org>
Date:   Mon, 24 Aug 2020 10:28:35 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Nicolas Prochazka <nicolas.prochazka@...il.com>,
        Tomoatsu Shimada <shimada@...brix.com>,
        Phillip Lougher <phillip@...ashfs.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Guenter Roeck <groeck@...omium.org>,
        Philippe Liard <pliard@...gle.com>,
        Christoph Hellwig <hch@....de>,
        Adrien Schildknecht <adrien+dev@...ischi.me>,
        Daniel Rosenberg <drosen@...gle.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 5.8 017/148] squashfs: avoid bio_alloc() failure with 1Mbyte blocks

From: Phillip Lougher <phillip@...ashfs.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@...il.com>
Reported-by: Tomoatsu Shimada <shimada@...brix.com>
Signed-off-by: Phillip Lougher <phillip@...ashfs.org.uk>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Reviewed-by: Guenter Roeck <groeck@...omium.org>
Cc: Philippe Liard <pliard@...gle.com>
Cc: Christoph Hellwig <hch@....de>
Cc: Adrien Schildknecht <adrien+dev@...ischi.me>
Cc: Daniel Rosenberg <drosen@...gle.com>
Cc: <stable@...r.kernel.org>
Link: http://lkml.kernel.org/r/20200815035637.15319-1-phillip@squashfs.org.uk
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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;