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DateThu, 02 Jul 2009 17:13:42 -0400
From"Doug Graham" <>
SubjectV3 minixfs bug
Is anybody interested in bugs in the minixfs V3 support that probably
only turn up on big-endian machines, or on filesystems with more than
64K inodes?

The problem is that that there are a few places (three that I've found)
where the "inode" field of a minix_dir_entry is used without checking
first to see if the dirent is really a minix3_dir_entry. The inode number
in a V1/V2 dirent is 16 bits, whereas that in a V3 dirent is 32 bits.
Accessing
it as a 16 bit field when it really should be accessed as a 32 bit field
probably kinda sorta works on a little-endian machine, but leads to some
rather odd behaviour on big-endian machines.

Here's a patch:

--- linux-2.6.29.2/fs/minix/dir.c 2009/07/02 21:05:33 1.1
+++ linux-2.6.29.2/fs/minix/dir.c 2009/07/02 21:10:31
@@ -311,14 +311,18 @@
struct inode *inode = (struct inode*)mapping->host;
char *kaddr = page_address(page);
loff_t pos = page_offset(page) + (char*)de - kaddr;
- unsigned len = minix_sb(inode->i_sb)->s_dirsize;
+ struct minix_sb_info *sbi = minix_sb(inode->i_sb);
+ unsigned len = sbi->s_dirsize;
int err;

lock_page(page);
err = __minix_write_begin(NULL, mapping, pos, len,
AOP_FLAG_UNINTERRUPTIBLE, &page,
NULL);
if (err == 0) {
- de->inode = 0;
+ if (sbi->s_version == MINIX_V3)
+ ((minix3_dirent *) de)->inode = 0;
+ else
+ de->inode = 0;
err = dir_commit_chunk(page, pos, len);
} else {
unlock_page(page);
@@ -443,7 +447,10 @@
err = __minix_write_begin(NULL, mapping, pos, sbi->s_dirsize,
AOP_FLAG_UNINTERRUPTIBLE, &page,
NULL);
if (err == 0) {
- de->inode = inode->i_ino;
+ if (sbi->s_version == MINIX_V3)
+ ((minix3_dirent *) de)->inode = inode->i_ino;
+ else
+ de->inode = inode->i_ino;
err = dir_commit_chunk(page, pos, sbi->s_dirsize);
} else {
unlock_page(page);
@@ -473,7 +480,14 @@
ino_t res = 0;

if (de) {
- res = de->inode;
+ struct address_space *mapping = page->mapping;
+ struct inode *inode = (struct inode*)mapping->host;
+ struct minix_sb_info *sbi = minix_sb(inode->i_sb);
+
+ if (sbi->s_version == MINIX_V3)
+ res = ((minix3_dirent *) de)->inode;
+ else
+ res = de->inode;
dir_put_page(page);
}
return res;

--Doug



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