6.6-stable review patch. If anyone has any objections, please let me know.
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From: Kees Cook keescook@chromium.org
[ 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 nathan@kernel.org Closes: https://github.com/ClangBuiltLinux/linux/issues/1966 [1] Link: https://github.com/llvm/llvm-project/issues/77813 [2] Cc: Steve French sfrench@samba.org Cc: Paulo Alcantara pc@manguebit.com Cc: Ronnie Sahlberg ronniesahlberg@gmail.com Cc: Shyam Prasad N sprasad@microsoft.com Cc: Tom Talpey tom@talpey.com Cc: linux-cifs@vger.kernel.org Cc: llvm@lists.linux.dev Signed-off-by: Kees Cook keescook@chromium.org Signed-off-by: Steve French stfrench@microsoft.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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 ef4c2e3c9fa61..6322f0f68a176 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,