linux-kernel - [PATCH] Guard check in module loader against integer overflow

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Message-ID: <20120522145613.32115.21217.stgit@warthog.procyon.org.uk>
Date:	Tue, 22 May 2012 15:56:13 +0100
From:	David Howells <dhowells@...hat.com>
To:	rusty@...tcorp.com.au
Cc:	linux-kernel@...r.kernel.org, David Howells <dhowells@...hat.com>
Subject: [PATCH] Guard check in module loader against integer overflow

The check:

	if (len < hdr->e_shoff + hdr->e_shnum * sizeof(Elf_Shdr))

may not work if there's an overflow in the right-hand side of the condition.

Signed-off-by: David Howells <dhowells@...hat.com>
---

 kernel/module.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)


diff --git a/kernel/module.c b/kernel/module.c
index 78ac6ec..377cb06 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2429,7 +2429,8 @@ static int copy_and_check(struct load_info *info,
 		goto free_hdr;
 	}
 
-	if (len < hdr->e_shoff + hdr->e_shnum * sizeof(Elf_Shdr)) {
+	if (hdr->e_shoff >= len ||
+	    hdr->e_shnum * sizeof(Elf_Shdr) > len - hdr->e_shoff) {
 		err = -ENOEXEC;
 		goto free_hdr;
 	}

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