[PATCH] stable: crypto: sha256 - fix crash at kexec

[Breno Leitao <leitao@debian.org>]

Loading a large (~2.1G) files with kexec crashes the host with when
running:

  # kexec --load kernel --initrd initrd_with_2G_or_more

  UBSAN: signed-integer-overflow in ./include/crypto/sha256_base.h:64:19
  34152083 * 64 cannot be represented in type 'int'
  ...
  BUG: unable to handle page fault for address: ff9fffff83b624c0
  sha256_update (lib/crypto/sha256.c:137)
  crypto_sha256_update (crypto/sha256_generic.c:40)
  kexec_calculate_store_digests (kernel/kexec_file.c:769)
  __se_sys_kexec_file_load (kernel/kexec_file.c:397 kernel/kexec_file.c:332)
  ...

(Line numbers based on commit da274362a7bd9 ("Linux 6.12.49")

This is not happening upstream (v6.16+), given that `block` type was
upgraded from "int" to "size_t" in commit 74a43a2cf5e8 ("crypto:
lib/sha256 - Move partial block handling out")

Upgrade the block type similar to the commit above, avoiding hitting the
overflow.

This patch is only suitable for the stable tree, and before 6.16, which
got commit 74a43a2cf5e8 ("crypto: lib/sha256 - Move partial block
handling out")

Signed-off-by: Breno Leitao <leitao@debian.org>
Fixes: 11b8d5ef9138 ("crypto: sha256 - implement base layer for SHA-256") # not after v6.16
Reported-by: Michael van der Westhuizen <rmikey@meta.com>
Reported-by: Tobias Fleig <tfleig@meta.com>
---
 include/crypto/sha256_base.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/crypto/sha256_base.h b/include/crypto/sha256_base.h
index e0418818d63c8..fa63af10102b2 100644
--- a/include/crypto/sha256_base.h
+++ b/include/crypto/sha256_base.h
@@ -44,7 +44,7 @@ static inline int lib_sha256_base_do_update(struct sha256_state *sctx,
 	sctx->count += len;
 
 	if (unlikely((partial + len) >= SHA256_BLOCK_SIZE)) {
-		int blocks;
+		size_t blocks;
 
 		if (partial) {
 			int p = SHA256_BLOCK_SIZE - partial;

---
base-commit: da274362a7bd9ab3a6e46d15945029145ebce672
change-id: 20251001-stable_crash-f2151baf043b

Best regards,
--  
Breno Leitao <leitao@debian.org>