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NFS: Prevent memory allocation failure in nfsacl_encode()

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nfsacl_encode() allocates memory in certain cases.  This of course
is not guaranteed to work.

Since commit 9f06c719 "SUNRPC: New xdr_streams XDR encoder API", the
kernel's XDR encoders can't return a result indicating possibly a
failure, so a memory allocation failure in nfsacl_encode() has become
fatal (ie, the XDR code Oopses) in some cases.

However, the allocated memory is a tiny fixed amount, on the order
of 40-50 bytes.  We can easily use a stack-allocated buffer for
this, with only a wee bit of nose-holding.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
This commit is contained in:
Chuck Lever 2011-01-21 03:05:38 +00:00 • committed by Trond Myklebust
parent 731f3f482a
commit f61f6da0d5
4 changed files with 31 additions and 13 deletions
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22
fs/nfs_common/nfsacl.c
View file

@ -42,6 +42,11 @@ struct nfsacl_encode_desc {
gid_t gid;
};
struct nfsacl_simple_acl {
struct posix_acl acl;
struct posix_acl_entry ace[4];
};
static int
xdr_nfsace_encode(struct xdr_array2_desc *desc, void *elem)
{
@ -99,17 +104,22 @@ int nfsacl_encode(struct xdr_buf *buf, unsigned int base, struct inode *inode,
.uid = inode->i_uid,
.gid = inode->i_gid,
};
struct nfsacl_simple_acl aclbuf;
int err;
struct posix_acl *acl2 = NULL;
if (entries > NFS_ACL_MAX_ENTRIES ||
xdr_encode_word(buf, base, entries))
return -EINVAL;
if (encode_entries && acl && acl->a_count == 3) {
/* Fake up an ACL_MASK entry. */
acl2 = posix_acl_alloc(4, GFP_KERNEL);
if (!acl2)
return -ENOMEM;
struct posix_acl *acl2 = &aclbuf.acl;
/* Avoid the use of posix_acl_alloc(). nfsacl_encode() is
* invoked in contexts where a memory allocation failure is
* fatal. Fortunately this fake ACL is small enough to
* construct on the stack. */
memset(acl2, 0, sizeof(acl2));
posix_acl_init(acl2, 4);
/* Insert entries in canonical order: other orders seem
to confuse Solaris VxFS. */
acl2->a_entries[0] = acl->a_entries[0]; /* ACL_USER_OBJ */
@ -120,8 +130,6 @@ int nfsacl_encode(struct xdr_buf *buf, unsigned int base, struct inode *inode,
nfsacl_desc.acl = acl2;
}
err = xdr_encode_array2(buf, base + 4, &nfsacl_desc.desc);
if (acl2)
posix_acl_release(acl2);
if (!err)
err = 8 + nfsacl_desc.desc.elem_size *
nfsacl_desc.desc.array_len;