Messages in this thread Patch in this message | | | From | David Howells <> | Subject | [PATCH] NFS: Check lengths more thoroughly in NFS4 readdir XDR decode | Date | Tue, 22 Aug 2006 17:19:53 +0100 |
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Check the bounds of length specifiers more thoroughly in the XDR decoding of NFS4 readdir reply data.
Currently, if the server returns a bitmap or attr length that causes the current decode point pointer to wrap, this could go undetected (consider a small "negative" length on a 32-bit machine).
Also add a check into the main XDR decode handler to make sure that the amount of data is a multiple of four bytes (as specified by RFC-1014). This makes sure that we can do u32* pointer subtraction in the NFS client without risking an undefined result (the result is undefined if the pointers are not correctly aligned with respect to one another).
Signed-Off-By: David Howells <dhowells@redhat.com> ---
fs/nfs/nfs4xdr.c | 22 +++++++++++----------- net/sunrpc/clnt.c | 11 +++++++++++ 2 files changed, 22 insertions(+), 11 deletions(-)
diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c index 992a713..41a295a 100644 --- a/fs/nfs/nfs4xdr.c +++ b/fs/nfs/nfs4xdr.c @@ -3355,7 +3355,7 @@ static int decode_readdir(struct xdr_str struct kvec *iov = rcvbuf->head; unsigned int nr, pglen = rcvbuf->page_len; uint32_t *end, *entry, *p, *kaddr; - uint32_t len, attrlen; + uint32_t len, attrlen, xlen; int hdrlen, recvd, status; status = decode_op_hdr(xdr, OP_READDIR); @@ -3374,13 +3374,12 @@ static int decode_readdir(struct xdr_str if (pglen > recvd) pglen = recvd; xdr_read_pages(xdr, pglen); - BUG_ON(pglen + readdir->pgbase > PAGE_CACHE_SIZE); kaddr = p = (uint32_t *) kmap_atomic(page, KM_USER0); - end = (uint32_t *) ((char *)p + pglen + readdir->pgbase); + end = p + ((pglen + readdir->pgbase) >> 2); entry = p; for (nr = 0; *p++; nr++) { - if (p + 3 > end) + if (end - p < 3) goto short_pkt; dprintk("cookie = %Lu, ", *((unsigned long long *)p)); p += 2; /* cookie */ @@ -3389,18 +3388,19 @@ static int decode_readdir(struct xdr_str printk(KERN_WARNING "NFS: giant filename in readdir (len 0x%x)\n", len); goto err_unmap; } - dprintk("filename = %*s\n", len, (char *)p); - p += XDR_QUADLEN(len); - if (p + 1 > end) + xlen = XDR_QUADLEN(len); + if (end - p < xlen) goto short_pkt; + dprintk("filename = %*s\n", len, (char *)p); + p += xlen; len = ntohl(*p++); /* bitmap length */ - p += len; - if (p + 1 > end) + if (end - p < len) goto short_pkt; + p += len; attrlen = XDR_QUADLEN(ntohl(*p++)); - p += attrlen; /* attributes */ - if (p + 2 > end) + if (end - p < attrlen + 1) goto short_pkt; + p += attrlen; /* attributes */ entry = p; } if (!nr && (entry[0] != 0 || entry[1] == 0)) diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c index d9eac70..3e19d32 100644 --- a/net/sunrpc/clnt.c +++ b/net/sunrpc/clnt.c @@ -1181,6 +1181,17 @@ call_verify(struct rpc_task *task) u32 *p = iov->iov_base, n; int error = -EACCES; + if ((task->tk_rqstp->rq_rcv_buf.len & 3) != 0) { + /* RFC-1014 says that the representation of XDR data must be a + * multiple of four bytes + * - if it isn't pointer subtraction in the NFS client may give + * undefined results + */ + printk(KERN_WARNING + "call_verify: XDR representation not a multiple of" + " 4 bytes: 0x%x\n", task->tk_rqstp->rq_rcv_buf.len); + goto out_eio; + } if ((len -= 3) < 0) goto out_overflow; p += 1; /* skip XID */ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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