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nfsd: Limit end of page list when decoding NFSv4 WRITE 

When processing an NFSv4 WRITE operation, argp->end should never
point past the end of the data in the final page of the page list.
Otherwise, nfsd4_decode_compound can walk into uninitialized memory.

More critical, nfsd4_decode_write is failing to increment argp->pagelen
when it increments argp->pagelist.  This can cause later xdr decoders
to assume more data is available than really is, which can cause server
crashes on malformed requests.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Cc: stable@vger.kernel.org
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
This commit is contained in:
Chuck Lever 2017-08-18 11:12:19 -04:00 committed by J. Bruce Fields
parent eff7936877
commit fc788f64f1
1 changed files with 2 additions and 4 deletions
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6
fs/nfsd/nfs4xdr.c
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@ -144,7 +144,7 @@ static void next_decode_page(struct nfsd4_compoundargs *argp)
argp->p = page_address(argp->pagelist[0]);
argp->pagelist++;
if (argp->pagelen < PAGE_SIZE) {
argp->end = argp->p + (argp->pagelen>>2);
argp->end = argp->p + XDR_QUADLEN(argp->pagelen);
argp->pagelen = 0;
} else {
argp->end = argp->p + (PAGE_SIZE>>2);
@ -1279,9 +1279,7 @@ nfsd4_decode_write(struct nfsd4_compoundargs *argp, struct nfsd4_write *write)
argp->pagelen -= pages * PAGE_SIZE;
len -= pages * PAGE_SIZE;
argp->p = (__be32 *)page_address(argp->pagelist[0]);
argp->pagelist++;
argp->end = argp->p + XDR_QUADLEN(PAGE_SIZE);
next_decode_page(argp);
}
argp->p += XDR_QUADLEN(len);