NFS: Check lengths more thoroughly in NFS4 readdir XDR decode
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>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
(cherry picked from 5861fddd64a7eaf7e8b1a9997455a24e7f688092 commit)
diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index 1750d99..730ec8f 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -3355,7 +3355,7 @@
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);
@@ -3377,10 +3377,10 @@
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 +3389,19 @@
printk(KERN_WARNING "NFS: giant filename in readdir (len 0x%x)\n", len);
goto err_unmap;
}
+ xlen = XDR_QUADLEN(len);
+ if (end - p < xlen + 1)
+ goto short_pkt;
dprintk("filename = %*s\n", len, (char *)p);
- p += XDR_QUADLEN(len);
- if (p + 1 > end)
- goto short_pkt;
+ p += xlen;
len = ntohl(*p++); /* bitmap length */
+ if (end - p < len + 1)
+ goto short_pkt;
p += len;
- if (p + 1 > end)
- goto short_pkt;
attrlen = XDR_QUADLEN(ntohl(*p++));
- p += attrlen; /* attributes */
- if (p + 2 > end)
+ if (end - p < attrlen + 2)
goto short_pkt;
+ p += attrlen; /* attributes */
entry = p;
}
if (!nr && (entry[0] != 0 || entry[1] == 0))