From 4af5dfb8dca3a6ad18feb6b2adcfffb4dc874e50 Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Tue, 10 Mar 2026 12:50:20 -0700 Subject: smb: client: Compare MACs in constant time commit 26bc83b88bbbf054f0980a4a42047a8d1e210e4c upstream. To prevent timing attacks, MAC comparisons need to be constant-time. Replace the memcmp() with the correct function, crypto_memneq(). Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Acked-by: Paulo Alcantara (Red Hat) Signed-off-by: Eric Biggers Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman --- fs/smb/client/cifsencrypt.c | 3 ++- fs/smb/client/smb2transport.c | 4 +++- 2 files changed, 5 insertions(+), 2 deletions(-) diff --git a/fs/smb/client/cifsencrypt.c b/fs/smb/client/cifsencrypt.c index 801824825ecf..b9e20bcaa8b5 100644 --- a/fs/smb/client/cifsencrypt.c +++ b/fs/smb/client/cifsencrypt.c @@ -26,6 +26,7 @@ #include #include #include +#include static int cifs_sig_update(struct cifs_calc_sig_ctx *ctx, const u8 *data, size_t len) @@ -277,7 +278,7 @@ int cifs_verify_signature(struct smb_rqst *rqst, /* cifs_dump_mem("what we think it should be: ", what_we_think_sig_should_be, 16); */ - if (memcmp(server_response_sig, what_we_think_sig_should_be, 8)) + if (crypto_memneq(server_response_sig, what_we_think_sig_should_be, 8)) return -EACCES; else return 0; diff --git a/fs/smb/client/smb2transport.c b/fs/smb/client/smb2transport.c index 6a9b80385b86..211305d43f8d 100644 --- a/fs/smb/client/smb2transport.c +++ b/fs/smb/client/smb2transport.c @@ -20,6 +20,7 @@ #include #include #include +#include #include "cifsglob.h" #include "cifsproto.h" #include "smb2proto.h" @@ -617,7 +618,8 @@ smb2_verify_signature(struct smb_rqst *rqst, struct TCP_Server_Info *server) if (rc) return rc; - if (memcmp(server_response_sig, shdr->Signature, SMB2_SIGNATURE_SIZE)) { + if (crypto_memneq(server_response_sig, shdr->Signature, + SMB2_SIGNATURE_SIZE)) { cifs_dbg(VFS, "sign fail cmd 0x%x message id 0x%llx\n", shdr->Command, shdr->MessageId); return -EACCES; -- cgit v1.2.3