[PATCH] image: Avoid erroneous double byte-swap in CRC value

[PATCH] image: Avoid erroneous double byte-swap in CRC value

[Alexandru Gagniuc]

The hash algorithm selection was streamlined in commit 92055e138f28
("image: Drop if/elseif hash selection in calculate_hash()"). Said
commit kept the call to cpu_to_uimage() to convert the CRC to big
endian format.

This would have been correct when calling crc32_wd(). However, the
->hash_func_ws member of crc32 points to crc32_wd_buf(), which already
converts the CRC to big endian. On a little endian host, doing both
conversions results in a little-endian CRC. This is incorrect.

To remedy this, simply drop the call to cpu_to_uimage(), thus only
doing the byte-order conversion once.

Fixes: 92055e138f28 ("image: Drop if/elseif hash selection in
       calculate_hash()")
Tested-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
---
 common/image-fit.c | 9 ---------
 1 file changed, 9 deletions(-)

diff --git a/common/image-fit.c b/common/image-fit.c
index 92d9141bcd..f02d437539 100644
--- a/common/image-fit.c
+++ b/common/image-fit.c
@@ -1193,12 +1193,6 @@ int fit_set_timestamp(void *fit, int noffset, time_t timestamp)
 	return 0;
 }
 
-static void crc32_uimage_fixup(void *value)
-{
-	/* TODO: In C, this type punning is undefined behavior: */
-	*((uint32_t *)value) = cpu_to_uimage(*((uint32_t *)value));
-}
-
 /**
  * calculate_hash - calculate and return hash for provided input data
  * @data: pointer to the input data
@@ -1232,9 +1226,6 @@ int calculate_hash(const void *data, int data_len, const char *name,
 	algo->hash_func_ws(data, data_len, value, algo->chunk_size);
 	*value_len = algo->digest_size;
 
-	if (!strcmp(name, "crc32"))
-		crc32_uimage_fixup(value);
-
 	return 0;
 }
 
-- 
2.31.1

Re: [PATCH] image: Avoid erroneous double byte-swap in CRC value

[Tom Rini]

[-- Attachment #1: Type: text/plain, Size: 948 bytes --]

On Tue, Sep 14, 2021 at 03:53:33PM -0500, Alexandru Gagniuc wrote:

> The hash algorithm selection was streamlined in commit 92055e138f28
> ("image: Drop if/elseif hash selection in calculate_hash()"). Said
> commit kept the call to cpu_to_uimage() to convert the CRC to big
> endian format.
> 
> This would have been correct when calling crc32_wd(). However, the
> ->hash_func_ws member of crc32 points to crc32_wd_buf(), which already
> converts the CRC to big endian. On a little endian host, doing both
> conversions results in a little-endian CRC. This is incorrect.
> 
> To remedy this, simply drop the call to cpu_to_uimage(), thus only
> doing the byte-order conversion once.
> 
> Fixes: 92055e138f28 ("image: Drop if/elseif hash selection in
>        calculate_hash()")
> Tested-by: Tom Rini <trini@konsulko.com>
> Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>

Applied to u-boot/master, thanks!

-- 
Tom

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 659 bytes --]