This is a note to let you know that I've just added the patch titled
fat: fix possible overflow for fat_clusters
to the 3.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
fat-fix-possible-overflow-for-fat_clusters.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 7b92d03c3239f43e5b86c9cc9630f026d36ee995 Mon Sep 17 00:00:00 2001
From: OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
Date: Fri, 24 May 2013 15:55:08 -0700
Subject: fat: fix possible overflow for fat_clusters
From: OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
commit 7b92d03c3239f43e5b86c9cc9630f026d36ee995 upstream.
Intermediate value of fat_clusters can be overflowed on 32bits arch.
Reported-by: Krzysztof Strasburger <strasbur@xxxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/fat/inode.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -1237,6 +1237,19 @@ static int fat_read_root(struct inode *i
return 0;
}
+static unsigned long calc_fat_clusters(struct super_block *sb)
+{
+ struct msdos_sb_info *sbi = MSDOS_SB(sb);
+
+ /* Divide first to avoid overflow */
+ if (sbi->fat_bits != 12) {
+ unsigned long ent_per_sec = sb->s_blocksize * 8 / sbi->fat_bits;
+ return ent_per_sec * sbi->fat_length;
+ }
+
+ return sbi->fat_length * sb->s_blocksize * 8 / sbi->fat_bits;
+}
+
/*
* Read the super block of an MS-DOS FS.
*/
@@ -1433,7 +1446,7 @@ int fat_fill_super(struct super_block *s
sbi->fat_bits = (total_clusters > MAX_FAT12) ? 16 : 12;
/* check that FAT table does not overflow */
- fat_clusters = sbi->fat_length * sb->s_blocksize * 8 / sbi->fat_bits;
+ fat_clusters = calc_fat_clusters(sb);
total_clusters = min(total_clusters, fat_clusters - FAT_START_ENT);
if (total_clusters > MAX_FAT(sb)) {
if (!silent)
Patches currently in stable-queue which might be from hirofumi@xxxxxxxxxxxxxxxxxx are
queue-3.4/fat-fix-possible-overflow-for-fat_clusters.patch
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