Re: [Xen-devel] [PATCH] LZ4 : fix the data abort issue

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Wed, 2015-03-25 at 16:14 +0000, Jan Beulich wrote:
> If the part of the compression data are corrupted, or the compression
> data is totally fake, the memory access over the limit is possible.
> 
> This is the log from my system usning lz4 decompression.
>    [6502]data abort, halting
>    [6503]r0  0x00000000 r1  0x00000000 r2  0xdcea0ffc r3  0xdcea0ffc
>    [6509]r4  0xb9ab0bfd r5  0xdcea0ffc r6  0xdcea0ff8 r7  0xdce80000
>    [6515]r8  0x00000000 r9  0x00000000 r10 0x00000000 r11 0xb9a98000
>    [6522]r12 0xdcea1000 usp 0x00000000 ulr 0x00000000 pc  0x820149bc
>    [6528]spsr 0x400001f3
> and the memory addresses of some variables at the moment are
>     ref:0xdcea0ffc, op:0xdcea0ffc, oend:0xdcea1000
> 
> As you can see, COPYLENGH is 8bytes, so @ref and @op can access the momory
> over @oend.
> 
> Signed-off-by: JeHyeon Yeon <tom.yeon@xxxxxxxxxxxxx>
> Reviewed-by: David Sterba <dsterba@xxxxxxx>
> [Linux commit d5e7cafd69da24e6d6cc988fab6ea313a2577efc]
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

> 
> --- a/xen/common/lz4/decompress.c
> +++ b/xen/common/lz4/decompress.c
> @@ -132,6 +132,9 @@ static int INIT lz4_uncompress(const uns
>                       /* Error: request to write beyond destination buffer */
>                       if (cpy > oend)
>                               goto _output_error;
> +                     if ((ref + COPYLENGTH) > oend ||
> +                                     (op + COPYLENGTH) > oend)
> +                             goto _output_error;
>                       LZ4_SECURECOPY(ref, op, (oend - COPYLENGTH));
>                       while (op < cpy)
>                               *op++ = *ref++;
> 
> 
> 



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