PROBLEM: Corrupt inode flags when remove ATTR_SYS flag on fat file system mounted with “sys_immutable” mount option.

DISCUSSION Dmitry Dmitriev 2 participants 2 messages May 31, 2011 – Jun 6, 2011 VFAT/FAT/msdos filesystem

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Dmitry Dmitriev

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2011-05-31 08:35 UTC #0 lore raw

Hello,

Inode flags are corrupted when removing ATTR_SYS flag by FAT_IOCTL_SET_ATTRIBUTES ioctl on fat file system mounted with “sys_immutable” mount option. In this case S_IMMUTABLE flag must be removed from inode flags, but actually removed all other flags except S_IMMUTABLE. This problem observed on 2.6.34 kernel, but it seems still exist( after examine of 2.6.39 kernel source code ).

The problem in fat_ioctl_set_attributes function( fs/fat/file.c ). This function contains following code(2.6.39 kernel):
101 if (sbi->options.sys_immutable) {
102 if (attr & ATTR_SYS)
103 inode->i_flags |= S_IMMUTABLE;
104 else
105 inode->i_flags &= S_IMMUTABLE;
106 }

Instead of removing S_IMMUTABLE flag from inode flags on line 105 function removes all other flags from inode flags. I think that line 105 must be following:

105 inode->i_flags &= ~S_IMMUTABLE;

Regards,
Dmitry

Andrew Morton

2011-06-06 23:51 UTC #1 lore raw

Quoted 12 lines · On Tue, 31 May 2011 12:27:24 +0400 Dmitry Dmitriev <[email protected]> wrote:

Hello,
Inode flags are corrupted when removing ATTR_SYS flag by FAT_IOCTL_SET_ATTRIBUTES ioctl on fat file system mounted with ___sys_immutable___ mount option. In this case S_IMMUTABLE flag must be removed from inode flags, but actually removed all other flags except S_IMMUTABLE. This problem observed on 2.6.34 kernel, but it seems still exist( after examine of 2.6.39 kernel source code ).
The problem in fat_ioctl_set_attributes function( fs/fat/file.c ). This function contains following code(2.6.39 kernel):
101 if (sbi->options.sys_immutable) {
102 if (attr & ATTR_SYS)
103 inode->i_flags |= S_IMMUTABLE;
104 else
105 inode->i_flags &= S_IMMUTABLE;
106 }

Quoted 4 lines

Instead of removing S_IMMUTABLE flag from inode flags on line 105 function removes all other flags from inode flags. I think that line 105 must be following:
105 inode->i_flags &= ~S_IMMUTABLE;

Thank, I queued this:

From: Andrew Morton <[email protected]>

Inode flags are corrupted when removing ATTR_SYS flag by FAT_IOCTL_SET_ATTRIBUTES ioctl on fat file system mounted with `sys_immutable' mount option.

Fix fat-fingered bitop from 21bea495943f9532 ("fat: split fat_generic_ioctl").

Reported-by Dmitry Dmitriev <[email protected]>

Cc Cristoph Hellwig <[email protected]>

Cc OGAWA Hirofumi <[email protected]>

Cc <[email protected]>

Signed-off-by Andrew Morton <[email protected]>

---

 fs/fat/file.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

fs/fat/file.c renamed from fs/fat/file.c~fs-fat-filec-fix-clearing-of-s_immutable +1 -1

diff -puN fs/fat/file.c~fs-fat-filec-fix-clearing-of-s_immutable fs/fat/file.c
@@ -102,7 +102,7 @@ static int fat_ioctl_set_attributes(stru
 		if (attr & ATTR_SYS)
 			inode->i_flags |= S_IMMUTABLE;
 		else
-			inode->i_flags &= S_IMMUTABLE;
+			inode->i_flags &= ~S_IMMUTABLE;
 	}
 
 	fat_save_attrs(inode, attr);