Re: Bug in caching of mount options

Mark Hemment (markhe@nextd.demon.co.uk)
Tue, 30 Sep 1997 18:13:16 +0100 (BST)

On Tue, 30 Sep 1997, Jim Nance wrote:
> If I mount a filesystem with the noexec option, then I (of cousre)
> cant run any binaries on it. If I remount it with:
>
> mount -o remount,exec /mnt/zip
>
> I can still not run binaries which I tried to run before the remount,
> but I CAN run new binaries which I copy into the file system.
>
> I can be more detailed if some one wants me to, but this is pretty
> easy to reproduce.

An inode structure caches the superblock flags (which include the noexec
mount option), in the member "i_flags".
When remounting "exec", only the superblock flags [s_flags] are updated.
Any 'cached' inodes still have the original flag value, which causes
IS_NOEXEC(inode) to return true.

The solution would be to parse the inode cache, and update "i_flags".
This code would belong in fs/inode.c, and would be similar to
invalidate_inodes() - although, obviously, there would be differences...

Regards,

markhe

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Mark Hemment, Unix/C Software Engineer (Contractor)
markhe@nextd.demon.co.uk http://www.nextd.demon.co.uk/
"Success has many fathers, failure is a B**TARD!" - anon
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