tools: kwboot: Fix sending very small images

Sending of very small images (smaller than 128 bytes = xmodem block size)
cause out-of-bound memory read access. Fix this issue by ensuring that
hdrsz when sending image is not larger than total size of the image.
Issue was introduced in commit f8017c37799c ("tools: kwboot: Fix sending
Kirkwood v0 images"). Special case when total image is smaller than header
size aligned to multiply of xmodem size is already handled since that
commit.

Fixes: f8017c37799c ("tools: kwboot: Fix sending Kirkwood v0 images")
Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Stefan Roese <sr@denx.de>

diff --git a/tools/kwboot.c b/tools/kwboot.c
index 61a9c3065aac6bf14c22f7e4efa0370804eadb8c..dc690636007d127d7eae895128a7ac9803156dc8 100644 (file)
--- a/tools/kwboot.c
+++ b/tools/kwboot.c
@@ -1455,6 +1455,8 @@ kwboot_xmodem(int tty, const void *_img, size_t size, int baudrate)
         * followed by the header. So align header size to xmodem block size.
         */
        hdrsz += (KWBOOT_XM_BLKSZ - hdrsz % KWBOOT_XM_BLKSZ) % KWBOOT_XM_BLKSZ;
+       if (hdrsz > size)
+               hdrsz = size;
 
        pnum = 1;