+ squashfs-fix-extending-readahead-beyond-end-of-file.patch added to mm-hotfixes-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: squashfs: fix extending readahead beyond end of file
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     squashfs-fix-extending-readahead-beyond-end-of-file.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/squashfs-fix-extending-readahead-beyond-end-of-file.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Phillip Lougher <phillip@squashfs.org.uk>
Subject: squashfs: fix extending readahead beyond end of file
Date: Thu, 20 Oct 2022 23:36:15 +0100

The readahead code will try to extend readahead to the entire size of the
Squashfs data block.

But, it didn't take into account that the last block at the end of the
file may not be a whole block.  In this case, the code would extend
readahead to beyond the end of the file, leaving trailing pages.

Fix this by only requesting the expected number of pages.

Link: https://lkml.kernel.org/r/20221020223616.7571-3-phillip@squashfs.org.uk
Fixes: 8fc78b6fe24c ("squashfs: implement readahead")
Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
Cc: <stable@vger.kernel.org>
Cc: Bagas Sanjaya <bagasdotme@gmail.com>
Cc: Dimitri John Ledkov <dimitri.ledkov@canonical.com>
Cc: Hsin-Yi Wang <hsinyi@chromium.org>
Cc: Mirsad Goran Todorovac <mirsad.todorovac@alu.unizg.hr>
Cc: Slade Watkins <srw@sladewatkins.net>
Cc: Thorsten Leemhuis <regressions@leemhuis.info>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/squashfs/file.c |   11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

--- a/fs/squashfs/file.c~squashfs-fix-extending-readahead-beyond-end-of-file
+++ a/fs/squashfs/file.c
@@ -559,6 +559,12 @@ static void squashfs_readahead(struct re
 		unsigned int expected;
 		struct page *last_page;
 
+		expected = start >> msblk->block_log == file_end ?
+			   (i_size_read(inode) & (msblk->block_size - 1)) :
+			    msblk->block_size;
+
+		max_pages = (expected + PAGE_SIZE - 1) >> PAGE_SHIFT;
+
 		nr_pages = __readahead_batch(ractl, pages, max_pages);
 		if (!nr_pages)
 			break;
@@ -567,13 +573,10 @@ static void squashfs_readahead(struct re
 			goto skip_pages;
 
 		index = pages[0]->index >> shift;
+
 		if ((pages[nr_pages - 1]->index >> shift) != index)
 			goto skip_pages;
 
-		expected = index == file_end ?
-			   (i_size_read(inode) & (msblk->block_size - 1)) :
-			    msblk->block_size;
-
 		if (index == file_end && squashfs_i(inode)->fragment_block !=
 						SQUASHFS_INVALID_BLK) {
 			res = squashfs_readahead_fragment(pages, nr_pages,
_

Patches currently in -mm which might be from phillip@squashfs.org.uk are

squashfs-fix-read-regression-introduced-in-readahead-code.patch
squashfs-fix-extending-readahead-beyond-end-of-file.patch
squashfs-fix-buffer-release-race-condition-in-readahead-code.patch