Commit f61f6da0 authored by Chuck Lever's avatar Chuck Lever Committed by Trond Myklebust
Browse files

NFS: Prevent memory allocation failure in nfsacl_encode() 



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: default avatarChuck Lever <chuck.lever@oracle.com>
Signed-off-by: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
parent 731f3f48

fs/nfs/nfs3acl.c

+2 −2
Original line number Diff line number Diff line
@@ -311,8 +311,8 @@ static int nfs3_proc_setacls(struct inode *inode, struct posix_acl *acl, 
	if (!nfs_server_capable(inode, NFS_CAP_ACLS))

		goto out;



	/* We are doing this here, because XDR marshalling can only

	   return -ENOMEM. */

	/* We are doing this here because XDR marshalling does not

	 * return any results, it BUGs. */

	status = -ENOSPC;

	if (acl != NULL && acl->a_count > NFS_ACL_MAX_ENTRIES)

		goto out;

fs/nfs_common/nfsacl.c

+15 −7
Original line number Diff line number Diff line
@@ -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;

fs/posix_acl.c

+13 −4
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@ 


#include <linux/errno.h>



EXPORT_SYMBOL(posix_acl_init);

EXPORT_SYMBOL(posix_acl_alloc);

EXPORT_SYMBOL(posix_acl_clone);

EXPORT_SYMBOL(posix_acl_valid);
@@ -31,6 +32,16 @@ EXPORT_SYMBOL(posix_acl_create_masq); 
EXPORT_SYMBOL(posix_acl_chmod_masq);

EXPORT_SYMBOL(posix_acl_permission);



/*

 * Init a fresh posix_acl

 */

void

posix_acl_init(struct posix_acl *acl, int count)

{

	atomic_set(&acl->a_refcount, 1);

	acl->a_count = count;

}



/*

 * Allocate a new ACL with the specified number of entries.

 */
@@ -40,10 +51,8 @@ posix_acl_alloc(int count, gfp_t flags) 
	const size_t size = sizeof(struct posix_acl) +

	                    count * sizeof(struct posix_acl_entry);

	struct posix_acl *acl = kmalloc(size, flags);

	if (acl) {

		atomic_set(&acl->a_refcount, 1);

		acl->a_count = count;

	}

	if (acl)

		posix_acl_init(acl, count);

	return acl;

}

include/linux/posix_acl.h

+1 −0
Original line number Diff line number Diff line
@@ -71,6 +71,7 @@ posix_acl_release(struct posix_acl *acl) 


/* posix_acl.c */



extern void posix_acl_init(struct posix_acl *, int);

extern struct posix_acl *posix_acl_alloc(int, gfp_t);

extern struct posix_acl *posix_acl_clone(const struct posix_acl *, gfp_t);

extern int posix_acl_valid(const struct posix_acl *);

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