linux-kernel - [PATCH 5.5 103/150] crypto: chacha20poly1305 - prevent integer overflow on large input

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Date:   Thu, 27 Feb 2020 14:37:20 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ard Biesheuvel <ardb@...nel.org>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Herbert Xu <herbert@...dor.apana.org.au>
Subject: [PATCH 5.5 103/150] crypto: chacha20poly1305 - prevent integer overflow on large input

From: Jason A. Donenfeld <Jason@...c4.com>

commit c9cc0517bba9f0213f1e55172feceb99e5512daf upstream.

This code assigns src_len (size_t) to sl (int), which causes problems
when src_len is very large. Probably nobody in the kernel should be
passing this much data to chacha20poly1305 all in one go anyway, so I
don't think we need to change the algorithm or introduce larger types
or anything. But we should at least error out early in this case and
print a warning so that we get reports if this does happen and can look
into why anybody is possibly passing it that much data or if they're
accidently passing -1 or similar.

Fixes: d95312a3ccc0 ("crypto: lib/chacha20poly1305 - reimplement crypt_from_sg() routine")
Cc: Ard Biesheuvel <ardb@...nel.org>
Cc: stable@...r.kernel.org # 5.5+
Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
Acked-by: Ard Biesheuvel <ardb@...nel.org>
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 lib/crypto/chacha20poly1305.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/lib/crypto/chacha20poly1305.c
+++ b/lib/crypto/chacha20poly1305.c
@@ -235,6 +235,9 @@ bool chacha20poly1305_crypt_sg_inplace(s
 		__le64 lens[2];
 	} b __aligned(16);

+	if (WARN_ON(src_len > INT_MAX))
+		return false;
+
 	chacha_load_key(b.k, key);

 	b.iv[0] = 0;