Subject: Re: [PATCH 01/15] ftruncate: pass a signed offset

From: Christian Brauner <[email-masked]>
Date: Fri, 21 Jun 2024 09:47:19 +0200

On Thu, Jun 20, 2024 at 06:23:02PM GMT, Arnd Bergmann wrote:
> From: Arnd Bergmann <[email-masked]>
> 
> The old ftruncate() syscall, using the 32-bit off_t misses a sign
> extension when called in compat mode on 64-bit architectures.  As a
> result, passing a negative length accidentally succeeds in truncating
> to file size between 2GiB and 4GiB.
> 
> Changing the type of the compat syscall to the signed compat_off_t
> changes the behavior so it instead returns -EINVAL.
> 
> The native entry point, the truncate() syscall and the corresponding
> loff_t based variants are all correct already and do not suffer
> from this mistake.
> 
> Fixes: 3f6d078d4acc ("fix compat truncate/ftruncate")
> Cc: [email-masked]
> Signed-off-by: Arnd Bergmann <[email-masked]>
> ---

Looks good to me,
Reviewed-by: Christian Brauner <[email-masked]>