From 8fbefa7a755d3481c80d621aec1f8feb447a18c1 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Tue, 23 Jan 2024 15:47:34 -0800 Subject: [PATCH] smb: Work around Clang __bdos() type confusion [ Upstream commit 8deb05c84b63b4fdb8549e08942867a68924a5b8 ] Recent versions of Clang gets confused about the possible size of the "user" allocation, and CONFIG_FORTIFY_SOURCE ends up emitting a warning[1]: repro.c:126:4: warning: call to '__write_overflow_field' declared with 'warning' attribute: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Wattribute-warning] 126 | __write_overflow_field(p_size_field, size); | ^ for this memset(): int len; __le16 *user; ... len = ses->user_name ? strlen(ses->user_name) : 0; user = kmalloc(2 + (len * 2), GFP_KERNEL); ... if (len) { ... } else { memset(user, '\0', 2); } While Clang works on this bug[2], switch to using a direct assignment, which avoids memset() entirely which both simplifies the code and silences the false positive warning. (Making "len" size_t also silences the warning, but the direct assignment seems better.) Reported-by: Nathan Chancellor Closes: https://github.com/ClangBuiltLinux/linux/issues/1966 [1] Link: https://github.com/llvm/llvm-project/issues/77813 [2] Cc: Steve French Cc: Paulo Alcantara Cc: Ronnie Sahlberg Cc: Shyam Prasad N Cc: Tom Talpey Cc: linux-cifs@vger.kernel.org Cc: llvm@lists.linux.dev Signed-off-by: Kees Cook Signed-off-by: Steve French Signed-off-by: Sasha Levin --- fs/smb/client/cifsencrypt.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/smb/client/cifsencrypt.c b/fs/smb/client/cifsencrypt.c index ef4c2e3c9fa6..6322f0f68a17 100644 --- a/fs/smb/client/cifsencrypt.c +++ b/fs/smb/client/cifsencrypt.c @@ -572,7 +572,7 @@ static int calc_ntlmv2_hash(struct cifs_ses *ses, char *ntlmv2_hash, len = cifs_strtoUTF16(user, ses->user_name, len, nls_cp); UniStrupr(user); } else { - memset(user, '\0', 2); + *(u16 *)user = 0; } rc = crypto_shash_update(ses->server->secmech.hmacmd5,