If a zero length is passed to kmalloc() it returns 0x10, which is
not a valid address. gss_verify_mic() subsequently crashes when it
attempts to dereference that pointer.
Instead of allocating this memory on every call based on an
untrusted size value, use a piece of dynamically-allocated scratch
memory that is always available.
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
net/sunrpc/auth_gss/svcauth_gss.c | 55 ++++++++++++++++++++++---------------
1 file changed, 32 insertions(+), 23 deletions(-)
diff --git a/net/sunrpc/auth_gss/svcauth_gss.c b/net/sunrpc/auth_gss/svcauth_gss.c
index 9a5db285d4ae..148bb0a7fa5b 100644
--- a/net/sunrpc/auth_gss/svcauth_gss.c
+++ b/net/sunrpc/auth_gss/svcauth_gss.c
@@ -49,11 +49,36 @@
#include <linux/sunrpc/svcauth.h>
#include <linux/sunrpc/svcauth_gss.h>
#include <linux/sunrpc/cache.h>
+#include <linux/sunrpc/gss_krb5.h>
#include <trace/events/rpcgss.h>
#include "gss_rpc_upcall.h"
+/*
+ * Unfortunately there isn't a maximum checksum size exported via the
+ * GSS API. Manufacture one based on GSS mechanisms supported by this
+ * implementation.
+ */
+#define GSS_MAX_CKSUMSIZE (GSS_KRB5_TOK_HDR_LEN + GSS_KRB5_MAX_CKSUM_LEN)
+
+/*
+ * This value may be increased in the future to accommodate other
+ * usage of the scratch buffer.
+ */
+#define GSS_SCRATCH_SIZE GSS_MAX_CKSUMSIZE
+
+struct gss_svc_data {
+ /* decoded gss client cred: */
+ struct rpc_gss_wire_cred clcred;
+ /* save a pointer to the beginning of the encoded verifier,
+ * for use in encryption/checksumming in svcauth_gss_release: */
+ __be32 *verf_start;
+ struct rsc *rsci;
+
+ /* for temporary results */
+ u8 gsd_scratch[GSS_SCRATCH_SIZE];
+};
/* The rpcsec_init cache is used for mapping RPCSEC_GSS_{,CONT_}INIT requests
* into replies.
@@ -887,13 +912,11 @@ read_u32_from_xdr_buf(struct xdr_buf *buf, int base, u32 *obj)
static int
unwrap_integ_data(struct svc_rqst *rqstp, struct xdr_buf *buf, u32 seq, struct gss_ctx *ctx)
{
+ struct gss_svc_data *gsd = rqstp->rq_auth_data;
u32 integ_len, rseqno, maj_stat;
- int stat = -EINVAL;
struct xdr_netobj mic;
struct xdr_buf integ_buf;
- mic.data = NULL;
-
/* NFS READ normally uses splice to send data in-place. However
* the data in cache can change after the reply's MIC is computed
* but before the RPC reply is sent. To prevent the client from
@@ -917,11 +940,9 @@ unwrap_integ_data(struct svc_rqst *rqstp, struct xdr_buf *buf, u32 seq, struct g
/* copy out mic... */
if (read_u32_from_xdr_buf(buf, integ_len, &mic.len))
goto unwrap_failed;
- if (mic.len > RPC_MAX_AUTH_SIZE)
- goto unwrap_failed;
- mic.data = kmalloc(mic.len, GFP_KERNEL);
- if (!mic.data)
+ if (mic.len > sizeof(gsd->gsd_scratch))
goto unwrap_failed;
+ mic.data = gsd->gsd_scratch;
if (read_bytes_from_xdr_buf(buf, integ_len + 4, mic.data, mic.len))
goto unwrap_failed;
maj_stat = gss_verify_mic(ctx, &integ_buf, &mic);
@@ -932,20 +953,17 @@ unwrap_integ_data(struct svc_rqst *rqstp, struct xdr_buf *buf, u32 seq, struct g
goto bad_seqno;
/* trim off the mic and padding at the end before returning */
xdr_buf_trim(buf, round_up_to_quad(mic.len) + 4);
- stat = 0;
-out:
- kfree(mic.data);
- return stat;
+ return 0;
unwrap_failed:
trace_rpcgss_svc_unwrap_failed(rqstp);
- goto out;
+ return -EINVAL;
bad_seqno:
trace_rpcgss_svc_seqno_bad(rqstp, seq, rseqno);
- goto out;
+ return -EINVAL;
bad_mic:
trace_rpcgss_svc_mic(rqstp, maj_stat);
- goto out;
+ return -EINVAL;
}
static inline int
@@ -1023,15 +1041,6 @@ unwrap_priv_data(struct svc_rqst *rqstp, struct xdr_buf *buf, u32 seq, struct gs
return -EINVAL;
}
-struct gss_svc_data {
- /* decoded gss client cred: */
- struct rpc_gss_wire_cred clcred;
- /* save a pointer to the beginning of the encoded verifier,
- * for use in encryption/checksumming in svcauth_gss_release: */
- __be32 *verf_start;
- struct rsc *rsci;
-};
-
static int
svcauth_gss_set_client(struct svc_rqst *rqstp)
{
