linux-kernel - [PATCH] binfmt_flat: Fix integer overflow bug on 32 bit systems

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Message-ID: <5be17f6c-5338-43be-91ef-650153b975cb@stanley.mountain>
Date: Wed, 4 Dec 2024 15:07:15 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Nicolas Pitre <npitre@...libre.com>
Cc: Alexander Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
	Kees Cook <kees@...nel.org>, Eric Biederman <ebiederm@...ssion.com>,
	linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH] binfmt_flat: Fix integer overflow bug on 32 bit systems

Most of these sizes and counts are capped at 256MB so the math doesn't
result in an integer overflow.  The "relocs" count needs to be checked
as well.  Otherwise on 32bit systems the calculation of "full_data"
could be wrong.

	full_data = data_len + relocs * sizeof(unsigned long);

Fixes: c995ee28d29d ("binfmt_flat: prevent kernel dammage from corrupted executable headers")
Cc: stable@...r.kernel.org
Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
---
 fs/binfmt_flat.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/binfmt_flat.c b/fs/binfmt_flat.c
index 390808ce935d..b5b5ca1a44f7 100644
--- a/fs/binfmt_flat.c
+++ b/fs/binfmt_flat.c
@@ -478,7 +478,7 @@ static int load_flat_file(struct linux_binprm *bprm,
 	 * 28 bits (256 MB) is way more than reasonable in this case.
 	 * If some top bits are set we have probable binary corruption.
 	*/
-	if ((text_len | data_len | bss_len | stack_len | full_data) >> 28) {
+	if ((text_len | data_len | bss_len | stack_len | relocs | full_data) >> 28) {
 		pr_err("bad header\n");
 		ret = -ENOEXEC;
 		goto err;
-- 
2.45.2