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authorTrond Myklebust <Trond.Myklebust@netapp.com>2012-08-26 11:44:43 -0700
committerTrond Myklebust <Trond.Myklebust@netapp.com>2012-09-06 11:11:53 -0400
commit1f1ea6c2d9d8c0be9ec56454b05315273b5de8ce (patch)
tree4718cdc2e494f18ab13c2c8f09930953b77c31ff
parent21f498c2f73bd6150d82931f09965826dca0b5f2 (diff)
downloadlinux-1f1ea6c2d9d8c0be9ec56454b05315273b5de8ce.tar.bz2
NFSv4: Fix buffer overflow checking in __nfs4_get_acl_uncached
Pass the checks made by decode_getacl back to __nfs4_get_acl_uncached so that it knows if the acl has been truncated. The current overflow checking is broken, resulting in Oopses on user-triggered nfs4_getfacl calls, and is opaque to the point where several attempts at fixing it have failed. This patch tries to clean up the code in addition to fixing the Oopses by ensuring that the overflow checks are performed in a single place (decode_getacl). If the overflow check failed, we will still be able to report the acl length, but at least we will no longer attempt to cache the acl or copy the truncated contents to user space. Reported-by: Sachin Prabhu <sprabhu@redhat.com> Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com> Tested-by: Sachin Prabhu <sprabhu@redhat.com>
-rw-r--r--fs/nfs/nfs4proc.c31
-rw-r--r--fs/nfs/nfs4xdr.c14
-rw-r--r--include/linux/nfs_xdr.h2
3 files changed, 18 insertions, 29 deletions
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 6b94f2d52532..1e50326d00dd 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -3739,7 +3739,7 @@ static void nfs4_write_cached_acl(struct inode *inode, struct page **pages, size
struct nfs4_cached_acl *acl;
size_t buflen = sizeof(*acl) + acl_len;
- if (pages && buflen <= PAGE_SIZE) {
+ if (buflen <= PAGE_SIZE) {
acl = kmalloc(buflen, GFP_KERNEL);
if (acl == NULL)
goto out;
@@ -3784,7 +3784,6 @@ static ssize_t __nfs4_get_acl_uncached(struct inode *inode, void *buf, size_t bu
};
unsigned int npages = DIV_ROUND_UP(buflen, PAGE_SIZE);
int ret = -ENOMEM, i;
- size_t acl_len = 0;
/* As long as we're doing a round trip to the server anyway,
* let's be prepared for a page of acl data. */
@@ -3807,11 +3806,6 @@ static ssize_t __nfs4_get_acl_uncached(struct inode *inode, void *buf, size_t bu
args.acl_len = npages * PAGE_SIZE;
args.acl_pgbase = 0;
- /* Let decode_getfacl know not to fail if the ACL data is larger than
- * the page we send as a guess */
- if (buf == NULL)
- res.acl_flags |= NFS4_ACL_LEN_REQUEST;
-
dprintk("%s buf %p buflen %zu npages %d args.acl_len %zu\n",
__func__, buf, buflen, npages, args.acl_len);
ret = nfs4_call_sync(NFS_SERVER(inode)->client, NFS_SERVER(inode),
@@ -3819,20 +3813,19 @@ static ssize_t __nfs4_get_acl_uncached(struct inode *inode, void *buf, size_t bu
if (ret)
goto out_free;
- acl_len = res.acl_len;
- if (acl_len > args.acl_len)
- nfs4_write_cached_acl(inode, NULL, 0, acl_len);
- else
- nfs4_write_cached_acl(inode, pages, res.acl_data_offset,
- acl_len);
- if (buf) {
+ /* Handle the case where the passed-in buffer is too short */
+ if (res.acl_flags & NFS4_ACL_TRUNC) {
+ /* Did the user only issue a request for the acl length? */
+ if (buf == NULL)
+ goto out_ok;
ret = -ERANGE;
- if (acl_len > buflen)
- goto out_free;
- _copy_from_pages(buf, pages, res.acl_data_offset,
- acl_len);
+ goto out_free;
}
- ret = acl_len;
+ nfs4_write_cached_acl(inode, pages, res.acl_data_offset, res.acl_len);
+ if (buf)
+ _copy_from_pages(buf, pages, res.acl_data_offset, res.acl_len);
+out_ok:
+ ret = res.acl_len;
out_free:
for (i = 0; i < npages; i++)
if (pages[i])
diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index 1bfbd67c556d..541e796e6db5 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -5072,18 +5072,14 @@ static int decode_getacl(struct xdr_stream *xdr, struct rpc_rqst *req,
* are stored with the acl data to handle the problem of
* variable length bitmaps.*/
res->acl_data_offset = xdr_stream_pos(xdr) - pg_offset;
-
- /* We ignore &savep and don't do consistency checks on
- * the attr length. Let userspace figure it out.... */
res->acl_len = attrlen;
- if (attrlen > (xdr->nwords << 2)) {
- if (res->acl_flags & NFS4_ACL_LEN_REQUEST) {
- /* getxattr interface called with a NULL buf */
- goto out;
- }
+
+ /* Check for receive buffer overflow */
+ if (res->acl_len > (xdr->nwords << 2) ||
+ res->acl_len + res->acl_data_offset > xdr->buf->page_len) {
+ res->acl_flags |= NFS4_ACL_TRUNC;
dprintk("NFS: acl reply: attrlen %u > page_len %u\n",
attrlen, xdr->nwords << 2);
- return -EINVAL;
}
} else
status = -EOPNOTSUPP;
diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
index ac7c8ae254f2..be9cf3c7e79e 100644
--- a/include/linux/nfs_xdr.h
+++ b/include/linux/nfs_xdr.h
@@ -652,7 +652,7 @@ struct nfs_getaclargs {
};
/* getxattr ACL interface flags */
-#define NFS4_ACL_LEN_REQUEST 0x0001 /* zero length getxattr buffer */
+#define NFS4_ACL_TRUNC 0x0001 /* ACL was truncated */
struct nfs_getaclres {
size_t acl_len;
size_t acl_data_offset;