SUNRPC: Revert 241b1f419f0e ("SUNRPC: Remove xdr_buf_trim()")

I've noticed that when krb5i or krb5p security is in use,
retransmitted requests are missing the server's duplicate reply
cache. The computed checksum on the retransmitted request does not
match the cached checksum, resulting in the server performing the
retransmitted request again instead of returning the cached reply.

The assumptions made when removing xdr_buf_trim() were not correct.
In the send paths, the upper layer has already set the segment
lengths correctly, and shorting the buffer's content is simply a
matter of reducing buf->len.

xdr_buf_trim() is the right answer in the receive/unwrap path on
both the client and the server. The buffer segment lengths have to
be shortened one-by-one.

On the server side in particular, head.iov_len needs to be updated
correctly to enable nfsd_cache_csum() to work correctly. The simple
buf->len computation doesn't do that, and that results in
checksumming stale data in the buffer.

The problem isn't noticed until there's significant instability of
the RPC transport. At that point, the reliability of retransmit
detection on the server becomes crucial.

Fixes: 241b1f419f0e ("SUNRPC: Remove xdr_buf_trim()")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

diff --git a/include/linux/sunrpc/xdr.h b/include/linux/sunrpc/xdr.h
index 01bb41908c93e22a7db40daeb3dff15b11ce9be1..22c207b2425fc2b4ef915b0dc591e094257c5970 100644 (file)
--- a/include/linux/sunrpc/xdr.h
+++ b/include/linux/sunrpc/xdr.h
@@ -184,6 +184,7 @@ xdr_adjust_iovec(struct kvec *iov, __be32 *p)
 extern void xdr_shift_buf(struct xdr_buf *, size_t);
 extern void xdr_buf_from_iov(struct kvec *, struct xdr_buf *);
 extern int xdr_buf_subsegment(struct xdr_buf *, struct xdr_buf *, unsigned int, unsigned int);
+extern void xdr_buf_trim(struct xdr_buf *, unsigned int);
 extern int read_bytes_from_xdr_buf(struct xdr_buf *, unsigned int, void *, unsigned int);
 extern int write_bytes_to_xdr_buf(struct xdr_buf *, unsigned int, void *, unsigned int);
 

diff --git a/net/sunrpc/auth_gss/gss_krb5_wrap.c b/net/sunrpc/auth_gss/gss_krb5_wrap.c
index 4905652e75679d33c5b249ca14096b7a0aa76cd7..cf0fd170ac1893193f79bdf78204343ae02f4ad6 100644 (file)
--- a/net/sunrpc/auth_gss/gss_krb5_wrap.c
+++ b/net/sunrpc/auth_gss/gss_krb5_wrap.c
@@ -580,15 +580,14 @@ gss_unwrap_kerberos_v2(struct krb5_ctx *kctx, int offset, int len,
         */
        movelen = min_t(unsigned int, buf->head[0].iov_len, len);
        movelen -= offset + GSS_KRB5_TOK_HDR_LEN + headskip;
-       if (offset + GSS_KRB5_TOK_HDR_LEN + headskip + movelen >
-           buf->head[0].iov_len)
-               return GSS_S_FAILURE;
+       BUG_ON(offset + GSS_KRB5_TOK_HDR_LEN + headskip + movelen >
+                                                       buf->head[0].iov_len);
        memmove(ptr, ptr + GSS_KRB5_TOK_HDR_LEN + headskip, movelen);
        buf->head[0].iov_len -= GSS_KRB5_TOK_HDR_LEN + headskip;
        buf->len = len - GSS_KRB5_TOK_HDR_LEN + headskip;
 
        /* Trim off the trailing "extra count" and checksum blob */
-       buf->len -= ec + GSS_KRB5_TOK_HDR_LEN + tailskip;
+       xdr_buf_trim(buf, ec + GSS_KRB5_TOK_HDR_LEN + tailskip);
 
        *align = XDR_QUADLEN(GSS_KRB5_TOK_HDR_LEN + headskip);
        *slack = *align + XDR_QUADLEN(ec + GSS_KRB5_TOK_HDR_LEN + tailskip);

diff --git a/net/sunrpc/auth_gss/svcauth_gss.c b/net/sunrpc/auth_gss/svcauth_gss.c
index d0a2f084e5a40ddb8e24113a3eac3fc613e14555..50d93c49ef1af670a0cd5bd82a4d69abaa926740 100644 (file)
--- a/net/sunrpc/auth_gss/svcauth_gss.c
+++ b/net/sunrpc/auth_gss/svcauth_gss.c
@@ -906,7 +906,7 @@ unwrap_integ_data(struct svc_rqst *rqstp, struct xdr_buf *buf, u32 seq, struct g
        if (svc_getnl(&buf->head[0]) != seq)
                goto out;
        /* trim off the mic and padding at the end before returning */
-       buf->len -= 4 + round_up_to_quad(mic.len);
+       xdr_buf_trim(buf, round_up_to_quad(mic.len) + 4);
        stat = 0;
 out:
        kfree(mic.data);

diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
index 15b58c5144f9eeaccb34a0525eaedac41f520f37..6f7d82fb1eb0a6748e37ab4e57d50650af7caa28 100644 (file)
--- a/net/sunrpc/xdr.c
+++ b/net/sunrpc/xdr.c
@@ -1150,6 +1150,47 @@ xdr_buf_subsegment(struct xdr_buf *buf, struct xdr_buf *subbuf,
 }
 EXPORT_SYMBOL_GPL(xdr_buf_subsegment);
 
+/**
+ * xdr_buf_trim - lop at most "len" bytes off the end of "buf"
+ * @buf: buf to be trimmed
+ * @len: number of bytes to reduce "buf" by
+ *
+ * Trim an xdr_buf by the given number of bytes by fixing up the lengths. Note
+ * that it's possible that we'll trim less than that amount if the xdr_buf is
+ * too small, or if (for instance) it's all in the head and the parser has
+ * already read too far into it.
+ */
+void xdr_buf_trim(struct xdr_buf *buf, unsigned int len)
+{
+       size_t cur;
+       unsigned int trim = len;
+
+       if (buf->tail[0].iov_len) {
+               cur = min_t(size_t, buf->tail[0].iov_len, trim);
+               buf->tail[0].iov_len -= cur;
+               trim -= cur;
+               if (!trim)
+                       goto fix_len;
+       }
+
+       if (buf->page_len) {
+               cur = min_t(unsigned int, buf->page_len, trim);
+               buf->page_len -= cur;
+               trim -= cur;
+               if (!trim)
+                       goto fix_len;
+       }
+
+       if (buf->head[0].iov_len) {
+               cur = min_t(size_t, buf->head[0].iov_len, trim);
+               buf->head[0].iov_len -= cur;
+               trim -= cur;
+       }
+fix_len:
+       buf->len -= (len - trim);
+}
+EXPORT_SYMBOL_GPL(xdr_buf_trim);
+
 static void __read_bytes_from_xdr_buf(struct xdr_buf *subbuf, void *obj, unsigned int len)
 {
        unsigned int this_len;