linux-hardening - [PATCH] coda: Avoid partial allocation of sig

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Date:   Fri, 27 Jan 2023 14:39:21 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Jan Harkes <jaharkes@...cmu.edu>
Cc:     Kees Cook <keescook@...omium.org>, coda@...cmu.edu,
        codalist@...a.cs.cmu.edu, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: [PATCH] coda: Avoid partial allocation of sig_inputArgs

GCC does not like having a partially allocation object, since it cannot
reason about it for bounds checking when it is passed to other code.
Instead, fully allocate sig_inputArgs. (Alternatively, sig_inputArgs
should be defined as a struct coda_in_hdr, if it is actually not using
any other part of the union.) Seen under GCC 13:

../fs/coda/upcall.c: In function 'coda_upcall':
../fs/coda/upcall.c:801:22: warning: array subscript 'union inputArgs[0]' is partly outside array bounds of 'unsigned char[20]' [-Warray-bounds=]
  801 |         sig_inputArgs->ih.opcode = CODA_SIGNAL;
      |                      ^~

Cc: Jan Harkes <jaharkes@...cmu.edu>
Cc: coda@...cmu.edu
Cc: codalist@...a.cs.cmu.edu
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 fs/coda/upcall.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/coda/upcall.c b/fs/coda/upcall.c
index 59f6cfd06f96..cd6a3721f6f6 100644
--- a/fs/coda/upcall.c
+++ b/fs/coda/upcall.c
@@ -791,7 +791,7 @@ static int coda_upcall(struct venus_comm *vcp,
 	sig_req = kmalloc(sizeof(struct upc_req), GFP_KERNEL);
 	if (!sig_req) goto exit;
 
-	sig_inputArgs = kvzalloc(sizeof(struct coda_in_hdr), GFP_KERNEL);
+	sig_inputArgs = kvzalloc(sizeof(*sig_inputArgs), GFP_KERNEL);
 	if (!sig_inputArgs) {
 		kfree(sig_req);
 		goto exit;
-- 
2.34.1