2012-06-29 18:23:43

by Steven J. Magnani

Subject: [PATCH v2] fat: Fix non-atomic NFS i_pos read

fat_encode_fh() can fetch an invalid i_pos value on systems
where 64-bit accesses are not atomic. Make it use the same
accessor as the rest of the FAT code.

Signed-off-by: Steven J. Magnani <[email protected]>
Acked-by: OGAWA Hirofumi <[email protected]>
---
diff -uprN linux-3.5-rc4/fs/fat/inode.c new/fs/fat/inode.c
--- linux-3.5-rc4/fs/fat/inode.c 2012-06-29 11:20:12.781348652 -0500
+++ new/fs/fat/inode.c 2012-06-29 13:18:13.712940800 -0500
@@ -738,22 +738,21 @@ static int
fat_encode_fh(struct inode *inode, __u32 *fh, int *lenp, struct inode *parent)
{
int len = *lenp;
- u32 ipos_h, ipos_m, ipos_l;
+ struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+ loff_t i_pos;

if (len < 5) {
*lenp = 5;
return 255; /* no room */
}

- ipos_h = MSDOS_I(inode)->i_pos >> 8;
- ipos_m = (MSDOS_I(inode)->i_pos & 0xf0) << 24;
- ipos_l = (MSDOS_I(inode)->i_pos & 0x0f) << 28;
+ i_pos = fat_i_pos_read(sbi, inode);
*lenp = 5;
fh[0] = inode->i_ino;
fh[1] = inode->i_generation;
- fh[2] = ipos_h;
- fh[3] = ipos_m | MSDOS_I(inode)->i_logstart;
- fh[4] = ipos_l;
+ fh[2] = i_pos >> 8;
+ fh[3] = ((i_pos & 0xf0) << 24) | MSDOS_I(inode)->i_logstart;
+ fh[4] = (i_pos & 0x0f) << 28;
if (parent)
fh[4] |= MSDOS_I(parent)->i_logstart;
return 3;

2012-06-29 18:54:28

by OGAWA Hirofumi

Subject: Re: [PATCH v2] fat: Fix non-atomic NFS i_pos read

"Steven J. Magnani" <[email protected]> writes:

> fat_encode_fh() can fetch an invalid i_pos value on systems
> where 64-bit accesses are not atomic. Make it use the same
> accessor as the rest of the FAT code.
>
> Signed-off-by: Steven J. Magnani <[email protected]>
> Acked-by: OGAWA Hirofumi <[email protected]>
> ---
> diff -uprN linux-3.5-rc4/fs/fat/inode.c new/fs/fat/inode.c
> --- linux-3.5-rc4/fs/fat/inode.c 2012-06-29 11:20:12.781348652 -0500
> +++ new/fs/fat/inode.c 2012-06-29 13:18:13.712940800 -0500
> @@ -738,22 +738,21 @@ static int
> fat_encode_fh(struct inode *inode, __u32 *fh, int *lenp, struct inode *parent)
> {
> int len = *lenp;
> - u32 ipos_h, ipos_m, ipos_l;
> + struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
> + loff_t i_pos;
>
> if (len < 5) {
> *lenp = 5;
> return 255; /* no room */
> }
>
> - ipos_h = MSDOS_I(inode)->i_pos >> 8;
> - ipos_m = (MSDOS_I(inode)->i_pos & 0xf0) << 24;
> - ipos_l = (MSDOS_I(inode)->i_pos & 0x0f) << 28;
> + i_pos = fat_i_pos_read(sbi, inode);
> *lenp = 5;
> fh[0] = inode->i_ino;
> fh[1] = inode->i_generation;
> - fh[2] = ipos_h;
> - fh[3] = ipos_m | MSDOS_I(inode)->i_logstart;
> - fh[4] = ipos_l;
> + fh[2] = i_pos >> 8;
> + fh[3] = ((i_pos & 0xf0) << 24) | MSDOS_I(inode)->i_logstart;
> + fh[4] = (i_pos & 0x0f) << 28;
> if (parent)
> fh[4] |= MSDOS_I(parent)->i_logstart;
> return 3;
>

--
OGAWA Hirofumi <[email protected]>