linux-kernel - [PATCH] afs: Annotate struct afs_addr_list with __counted

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Date:   Fri, 15 Sep 2023 13:14:49 -0700
From:   Kees Cook <keescook@...omium.org>
To:     David Howells <dhowells@...hat.com>
Cc:     Kees Cook <keescook@...omium.org>,
        Marc Dionne <marc.dionne@...istor.com>,
        linux-afs@...ts.infradead.org,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, linux-hardening@...r.kernel.org
Subject: [PATCH] afs: Annotate struct afs_addr_list with __counted_by

Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
(for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

As found with Coccinelle[1], add __counted_by for struct afs_addr_list.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc: David Howells <dhowells@...hat.com>
Cc: Marc Dionne <marc.dionne@...istor.com>
Cc: linux-afs@...ts.infradead.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 fs/afs/internal.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index da73b97e19a9..07433a5349ca 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -87,7 +87,7 @@ struct afs_addr_list {
 	enum dns_lookup_status	status:8;
 	unsigned long		failed;		/* Mask of addrs that failed locally/ICMP */
 	unsigned long		responded;	/* Mask of addrs that responded */
-	struct sockaddr_rxrpc	addrs[];
+	struct sockaddr_rxrpc	addrs[] __counted_by(max_addrs);
 #define AFS_MAX_ADDRESSES ((unsigned int)(sizeof(unsigned long) * 8))
 };
 
-- 
2.34.1