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SUNRPC: Fix ("SUNRPC: Add "@len" parameter to gss_unwrap()") 

[ Upstream commit 986a4b63d3 ]

Braino when converting "buf->len -=" to "buf->len = len -".

The result is under-estimation of the ralign and rslack values. On
krb5p mounts, this has caused READDIR to fail with EIO, and KASAN
splats when decoding READLINK replies.

As a result of fixing this oversight, the gss_unwrap method now
returns a buf->len that can be shorter than priv_len for small
RPC messages. The additional adjustment done in unwrap_priv_data()
can underflow buf->len. This causes the nfsd_request_too_large
check to fail during some NFSv3 operations.

Reported-by: Marian Rainer-Harbach
Reported-by: Pierre Sauter <pierre.sauter@stwm.de>
BugLink: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1886277
Fixes: 31c9590ae4 ("SUNRPC: Add "@len" parameter to gss_unwrap()")
Reviewed-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Chuck Lever 2020-07-24 17:08:57 -04:00 committed by Greg Kroah-Hartman
parent 789be9705e
commit 18d1bb4973
2 changed files with 1 additions and 2 deletions
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2
net/sunrpc/auth_gss/gss_krb5_wrap.c
View File

@ -584,7 +584,7 @@ gss_unwrap_kerberos_v2(struct krb5_ctx *kctx, int offset, int len,
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;
buf->len = len - (GSS_KRB5_TOK_HDR_LEN + headskip);
/* Trim off the trailing "extra count" and checksum blob */
xdr_buf_trim(buf, ec + GSS_KRB5_TOK_HDR_LEN + tailskip);

1
net/sunrpc/auth_gss/svcauth_gss.c
View File

@ -949,7 +949,6 @@ unwrap_priv_data(struct svc_rqst *rqstp, struct xdr_buf *buf, u32 seq, struct gs
maj_stat = gss_unwrap(ctx, 0, priv_len, buf);
pad = priv_len - buf->len;
buf->len -= pad;
/* The upper layers assume the buffer is aligned on 4-byte boundaries.
* In the krb5p case, at least, the data ends up offset, so we need to
* move it around. */