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SubjectRe: [PATCH] Fix read buffer overflow in delta-ipc
Date
Hi Andi,
Thanks for the patch but I would suggest to use strlcpy instead, this
will guard msg.name overwriting and add the NULL termination in case
of truncation:
- memcpy(msg.name, name, sizeof(msg.name));
- msg.name[sizeof(msg.name) - 1] = 0;
+ strlcpy(msg.name, name, sizeof(msg.name));

Best regards,
Hugues.

On 12/22/2017 01:12 AM, Andi Kleen wrote:
> From: Andi Kleen <ak@linux.intel.com>
>
> The single caller passes a string to delta_ipc_open, which copies with a
> fixed size larger than the string. So it copies some random data after
> the original string the ro segment.
>
> If the string was at the end of a page it may fault.
>
> Just copy the string with a normal strcpy after clearing the field.
>
> Found by a LTO build (which errors out)
> because the compiler inlines the functions and can resolve
> the string sizes and triggers the compile time checks in memcpy.
>
> In function ‘memcpy’,
> inlined from ‘delta_ipc_open.constprop’ at linux/drivers/media/platform/sti/delta/delta-ipc.c:178:0,
> inlined from ‘delta_mjpeg_ipc_open’ at linux/drivers/media/platform/sti/delta/delta-mjpeg-dec.c:227:0,
> inlined from ‘delta_mjpeg_decode’ at linux/drivers/media/platform/sti/delta/delta-mjpeg-dec.c:403:0:
> /home/andi/lsrc/linux/include/linux/string.h:337:0: error: call to ‘__read_overflow2’ declared with attribute error: detected read beyond size of object passed as 2nd parameter
> __read_overflow2();
>
> Cc: hugues.fruchet@st.com
> Cc: mchehab@s-opensource.com
> Signed-off-by: Andi Kleen <ak@linux.intel.com>
> ---
> drivers/media/platform/sti/delta/delta-ipc.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/media/platform/sti/delta/delta-ipc.c b/drivers/media/platform/sti/delta/delta-ipc.c
> index 41e4a4c259b3..b6c256e3ceb6 100644
> --- a/drivers/media/platform/sti/delta/delta-ipc.c
> +++ b/drivers/media/platform/sti/delta/delta-ipc.c
> @@ -175,8 +175,8 @@ int delta_ipc_open(struct delta_ctx *pctx, const char *name,
> msg.ipc_buf_size = ipc_buf_size;
> msg.ipc_buf_paddr = ctx->ipc_buf->paddr;
>
> - memcpy(msg.name, name, sizeof(msg.name));
> - msg.name[sizeof(msg.name) - 1] = 0;
> + memset(msg.name, 0, sizeof(msg.name));
> + strcpy(msg.name, name);
>
> msg.param_size = param->size;
> memcpy(ctx->ipc_buf->vaddr, param->data, msg.param_size);
>
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