+ fs-ntfs3-fix-negative-shift-size-in-true_sectors_per_clst.patch added to mm-nonmm-unstable branch

+ fs-ntfs3-fix-negative-shift-size-in-true_sectors_per_clst.patch added to mm-nonmm-unstable branch

[Andrew Morton]

The patch titled
     Subject: fs/ntfs3: fix negative shift size in true_sectors_per_clst()
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     fs-ntfs3-fix-negative-shift-size-in-true_sectors_per_clst.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/fs-ntfs3-fix-negative-shift-size-in-true_sectors_per_clst.patch

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

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------------------------------------------------------
From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Subject: fs/ntfs3: fix negative shift size in true_sectors_per_clst()
Date: Wed, 21 Sep 2022 00:59:27 +0900

syzbot is reporting shift-out-of-bounds in true_sectors_per_clst() [1],
for commit a3b774342fa752a5 ("fs/ntfs3: validate BOOT
sectors_per_clusters") did not address that (0 -
boot->sectors_per_clusters) < 0 because "u8" was chosen for type of
boot->sectors_per_clusters because 0x80 needs to be positive in order to
support 64K clusters.  Use "s8" cast in order to make sure that (0 - (s8)
boot->sectors_per_clusters) > 0.

Link: https://syzkaller.appspot.com/bug?extid=1631f09646bc214d2e76 [1]
Link: https://lkml.kernel.org/r/4b37f037-3b10-b4e4-0644-73441c8fa0af@I-love.SAKURA.ne.jp
Fixes: a3b774342fa752a5 ("fs/ntfs3: validate BOOT sectors_per_clusters")
Reported-by: syzbot <syzbot+1631f09646bc214d2e76@syzkaller.appspotmail.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Tested-by: syzbot <syzbot+1631f09646bc214d2e76@syzkaller.appspotmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---


--- a/fs/ntfs3/super.c~fs-ntfs3-fix-negative-shift-size-in-true_sectors_per_clst
+++ a/fs/ntfs3/super.c
@@ -672,7 +672,7 @@ static u32 true_sectors_per_clst(const s
 	if (boot->sectors_per_clusters <= 0x80)
 		return boot->sectors_per_clusters;
 	if (boot->sectors_per_clusters >= 0xf4) /* limit shift to 2MB max */
-		return 1U << (0 - boot->sectors_per_clusters);
+		return 1U << (0 - (s8) boot->sectors_per_clusters);
 	return -EINVAL;
 }
 
_

Patches currently in -mm which might be from penguin-kernel@I-love.SAKURA.ne.jp are

fs-ntfs3-fix-negative-shift-size-in-true_sectors_per_clst.patch