fs/sysv: v7: adjust sanity checks for some volumes

Newly mkfs-ed filesystems from Seventh Edition have last modification time
set to zero, but are otherwise perfectly valid.

Also, tighten up other sanity checks to filter out most filesystems with

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/sysv/super.c b/fs/sysv/super.c
index 2da3075..3785262 100644 (file)
--- a/fs/sysv/super.c
+++ b/fs/sysv/super.c
@@ -469,7 +469,7 @@ static int v7_fill_super(struct super_block *sb, void *data, int silent)
        v7sb = (struct v7_super_block *) bh->b_data;
        if (fs16_to_cpu(sbi, v7sb->s_nfree) > V7_NICFREE ||
            fs16_to_cpu(sbi, v7sb->s_ninode) > V7_NICINOD ||
-           fs32_to_cpu(sbi, v7sb->s_time) == 0)
+           fs32_to_cpu(sbi, v7sb->s_fsize) > V7_MAXSIZE)
                goto failed;
 
        /* plausibility check on root inode: it is a directory,
@@ -479,7 +479,9 @@ static int v7_fill_super(struct super_block *sb, void *data, int silent)
        v7i = (struct sysv_inode *)(bh2->b_data + 64);
        if ((fs16_to_cpu(sbi, v7i->i_mode) & ~0777) != S_IFDIR ||
            (fs32_to_cpu(sbi, v7i->i_size) == 0) ||
-           (fs32_to_cpu(sbi, v7i->i_size) & 017) != 0)
+           (fs32_to_cpu(sbi, v7i->i_size) & 017) ||
+           (fs32_to_cpu(sbi, v7i->i_size) > V7_NFILES *
+            sizeof(struct sysv_dir_entry)))
                goto failed;
        brelse(bh2);
        bh2 = NULL;

diff --git a/include/linux/sysv_fs.h b/include/linux/sysv_fs.h
index 9641130..e47d6d9 100644 (file)
--- a/include/linux/sysv_fs.h
+++ b/include/linux/sysv_fs.h
@@ -148,6 +148,17 @@ struct v7_super_block {
        char    s_fname[6];     /* file system name */
        char    s_fpack[6];     /* file system pack name */
 };
+/* Constants to aid sanity checking */
+/* This is not a hard limit, nor enforced by v7 kernel. It's actually just
+ * the limit used by Seventh Edition's ls, though is high enough to assume
+ * that no reasonable file system would have that much entries in root
+ * directory. Thus, if we see anything higher, we just probably got the
+ * endiannes wrong. */
+#define V7_NFILES      1024
+/* The disk addresses are three-byte (despite direct block addresses being
+ * aligned word-wise in inode). If the most significant byte is non-zero,
+ * something is most likely wrong (not a filesystem, bad bytesex). */
+#define V7_MAXSIZE     0x00ffffff
 
 /* Coherent super-block data on disk */
 #define COH_NICINOD    100     /* number of inode cache entries */