asn1: additional sanity checking during BER decoding
- Don't trust a length which is greater than the working buffer.
An invalid length could cause overflow when calculating buffer size
for decoding oid.
- An oid length of zero is invalid and allows for an off-by-one error when
decoding oid because the first subid actually encodes first 2 subids.
- A primitive encoding may not have an indefinite length.
Thanks to Wei Wang from McAfee for report.
Cc: Steven French <sfrench@us.ibm.com>
Cc: stable@kernel.org
Acked-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/cifs/asn1.c b/fs/cifs/asn1.c
index cb52cbb..f58e41d 100644
--- a/fs/cifs/asn1.c
+++ b/fs/cifs/asn1.c
@@ -186,6 +186,11 @@
}
}
}
+
+ /* don't trust len bigger than ctx buffer */
+ if (*len > ctx->end - ctx->pointer)
+ return 0;
+
return 1;
}
@@ -203,6 +208,10 @@
if (!asn1_length_decode(ctx, &def, &len))
return 0;
+ /* primitive shall be definite, indefinite shall be constructed */
+ if (*con == ASN1_PRI && !def)
+ return 0;
+
if (def)
*eoc = ctx->pointer + len;
else
@@ -389,6 +398,11 @@
unsigned long *optr;
size = eoc - ctx->pointer + 1;
+
+ /* first subid actually encodes first two subids */
+ if (size < 2 || size > ULONG_MAX/sizeof(unsigned long))
+ return 0;
+
*oid = kmalloc(size * sizeof(unsigned long), GFP_ATOMIC);
if (*oid == NULL)
return 0;