[PATCH] Fix read buffer overflow in delta-ipc

[Andi Kleen]

From: Andi Kleen <ak@xxxxxxxxxxxxxxx>

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 âmemcpyâ,
    inlined from âdelta_ipc_open.constpropâ at linux/drivers/media/platform/sti/delta/delta-ipc.c:178:0,
    inlined from âdelta_mjpeg_ipc_openâ at linux/drivers/media/platform/sti/delta/delta-mjpeg-dec.c:227:0,
    inlined from âdelta_mjpeg_decodeâ 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 â__read_overflow2â declared with attribute error: detected read beyond size of object passed as 2nd parameter
    __read_overflow2();

Cc: hugues.fruchet@xxxxxx
Cc: mchehab@xxxxxxxxxxxxxxxx
Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
---
 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);
-- 
2.15.0