Re: [PATCH] /dev/mem: handle out-of-bounds read/write

[Greg Kroah-Hartman]

On Thu, Jan 30, 2014 at 09:48:02AM +0100, Petr Tesarik wrote:
> The loff_t type may be wider than phys_addr_t (e.g. on 32-bit systems).
> Consequently, the file offset may be truncated in the assignment.
> Currently, /dev/mem wraps around, which may cause applications to read
> or write incorrect regions of memory by accident.

Does that really happen?  If so, that's a userspace bug, right?

> Let's follow POSIX file semantics here and return 0 when reading from
> and -EFBIG when writing to an offset that cannot be represented by a
> phys_addr_t.
> 
> Note that the conditional is optimized out by the compiler if loff_t
> has the same size as phys_addr_t.
> 
> Signed-off-by: Petr Tesarik <ptesarik@xxxxxxx>
> ---
>  drivers/char/mem.c | 6 ++++++
>  1 file changed, 6 insertions(+)

What is going to break if we apply this patch?  :)

thanks,

greg k-h
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/