Messages in this thread Patch in this message | | | Date | Wed, 03 Jul 2013 14:39:14 -0400 | From | Steven Rostedt <> | Subject | [017/141] fat: fix possible overflow for fat_clusters |
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3.6.11.6 stable review patch. If anyone has any objections, please let me know.
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From: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
[ Upstream commit 7b92d03c3239f43e5b86c9cc9630f026d36ee995 ]
Intermediate value of fat_clusters can be overflowed on 32bits arch.
Reported-by: Krzysztof Strasburger <strasbur@chkw386.ch.pwr.wroc.pl> Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> --- fs/fat/inode.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/fs/fat/inode.c b/fs/fat/inode.c index 05e897f..ca5241f 100644 --- a/fs/fat/inode.c +++ b/fs/fat/inode.c @@ -1212,6 +1212,19 @@ static int fat_read_root(struct inode *inode) 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. */ @@ -1409,7 +1422,7 @@ int fat_fill_super(struct super_block *sb, void *data, int silent, int isvfat, 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) -- 1.7.10.4
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