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@xxxxxxxxxx>
---
fs/nfs/nfs3acl.c | 4 ++--
fs/nfs_common/nfsacl.c | 22 +++++++++++++++-------
fs/posix_acl.c | 17 +++++++++++++----
include/linux/posix_acl.h | 1 +
4 files changed, 31 insertions(+), 13 deletions(-)
diff --git a/fs/nfs/nfs3acl.c b/fs/nfs/nfs3acl.c
index 9f88c5f..2743427 100644
--- a/fs/nfs/nfs3acl.c
+++ b/fs/nfs/nfs3acl.c
@@ -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;
diff --git a/fs/nfs_common/nfsacl.c b/fs/nfs_common/nfsacl.c
index a3e78bd..84c27d6 100644
--- a/fs/nfs_common/nfsacl.c
+++ b/fs/nfs_common/nfsacl.c
@@ -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;
diff --git a/fs/posix_acl.c b/fs/posix_acl.c
index 39df95a..b1cf6bf 100644
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -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);
@@ -32,6 +33,16 @@ 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.
*/
struct posix_acl *
@@ -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;
}
diff --git a/include/linux/posix_acl.h b/include/linux/posix_acl.h
index d68283a..54211c1 100644
--- a/include/linux/posix_acl.h
+++ b/include/linux/posix_acl.h
@@ -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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