linux-kernel - [ 46/47] Avoid beyond bounds copy while caching ACL

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Message-Id: <20120518212653.363629474@linuxfoundation.org>
Date:	Fri, 18 May 2012 14:27:35 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Sachin Prabhu <sprabhu@...hat.com>,
	Jian Li <jiali@...hat.com>,
	Trond Myklebust <Trond.Myklebust@...app.com>
Subject: [ 46/47] Avoid beyond bounds copy while caching ACL

3.3-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Sachin Prabhu <sprabhu@...hat.com>

commit 5794d21ef4639f0e33440927bb903f9598c21e92 upstream.

When attempting to cache ACLs returned from the server, if the bitmap
size + the ACL size is greater than a PAGE_SIZE but the ACL size itself
is smaller than a PAGE_SIZE, we can read past the buffer page boundary.

Signed-off-by: Sachin Prabhu <sprabhu@...hat.com>
Reported-by: Jian Li <jiali@...hat.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@...app.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/nfs/nfs4proc.c |   12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -3532,16 +3532,16 @@ out:
 	return ret;
 }
 
-static void nfs4_write_cached_acl(struct inode *inode, const char *buf, size_t acl_len)
+static void nfs4_write_cached_acl(struct inode *inode, struct page **pages, size_t pgbase, size_t acl_len)
 {
 	struct nfs4_cached_acl *acl;
 
-	if (buf && acl_len <= PAGE_SIZE) {
+	if (pages && acl_len <= PAGE_SIZE) {
 		acl = kmalloc(sizeof(*acl) + acl_len, GFP_KERNEL);
 		if (acl == NULL)
 			goto out;
 		acl->cached = 1;
-		memcpy(acl->data, buf, acl_len);
+		_copy_from_pages(acl->data, pages, pgbase, acl_len);
 	} else {
 		acl = kmalloc(sizeof(*acl), GFP_KERNEL);
 		if (acl == NULL)
@@ -3574,7 +3574,6 @@ static ssize_t __nfs4_get_acl_uncached(s
 	struct nfs_getaclres res = {
 		.acl_len = buflen,
 	};
-	void *resp_buf;
 	struct rpc_message msg = {
 		.rpc_proc = &nfs4_procedures[NFSPROC4_CLNT_GETACL],
 		.rpc_argp = &args,
@@ -3605,7 +3604,6 @@ static ssize_t __nfs4_get_acl_uncached(s
 	 * the page we send as a guess */
 	if (buf == NULL)
 		res.acl_flags |= NFS4_ACL_LEN_REQUEST;
-	resp_buf = page_address(pages[0]);
 
 	dprintk("%s  buf %p buflen %zu npages %d args.acl_len %zu\n",
 		__func__, buf, buflen, npages, args.acl_len);
@@ -3616,9 +3614,9 @@ static ssize_t __nfs4_get_acl_uncached(s
 
 	acl_len = res.acl_len - res.acl_data_offset;
 	if (acl_len > args.acl_len)
-		nfs4_write_cached_acl(inode, NULL, acl_len);
+		nfs4_write_cached_acl(inode, NULL, 0, acl_len);
 	else
-		nfs4_write_cached_acl(inode, resp_buf + res.acl_data_offset,
+		nfs4_write_cached_acl(inode, pages, res.acl_data_offset,
 				      acl_len);
 	if (buf) {
 		ret = -ERANGE;


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