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Subject[10/90] ext4: reject too-large filesystems on 32-bit kernels
2.6.31-stable review patch.  If anyone has any objections, please let us know.

------------------
(cherry picked from commit bf43d84b185e2ff54598f8c58a5a8e63148b6e90)
ext4 will happily mount a > 16T filesystem on a 32-bit box, but
this is not safe; writes to the block device will wrap past 16T
and the page cache can't index past 16T (232 index * 4k pages).
Adding another test to the existing "too many sectors" test
should do the trick.

Add a comment, a relevant return value, and fix the reference
to the CONFIG_LBD(AF) option as well.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
fs/ext4/super.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2550,12 +2550,19 @@ static int ext4_fill_super(struct super_
goto failed_mount;
}

- if (ext4_blocks_count(es) >
- (sector_t)(~0ULL) >> (sb->s_blocksize_bits - 9)) {
+ /*
+ * Test whether we have more sectors than will fit in sector_t,
+ * and whether the max offset is addressable by the page cache.
+ */
+ if ((ext4_blocks_count(es) >
+ (sector_t)(~0ULL) >> (sb->s_blocksize_bits - 9)) ||
+ (ext4_blocks_count(es) >
+ (pgoff_t)(~0ULL) >> (PAGE_CACHE_SHIFT - sb->s_blocksize_bits))) {
ext4_msg(sb, KERN_ERR, "filesystem"
- " too large to mount safely");
+ " too large to mount safely on this system");
if (sizeof(sector_t) < 8)
ext4_msg(sb, KERN_WARNING, "CONFIG_LBDAF not enabled");
+ ret = -EFBIG;
goto failed_mount;
}




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