dlm: fix length calculation in compat code
Using offsetof() to calculate name length does not work because
it does not produce consistent results with with structure packing.
This caused memcpy to corrupt memory by copying 4 extra bytes off
the end of the buffer on 64 bit kernels with 32 bit userspace
(the only case where this 32/64 compat code is used).
The fix is to calculate name length directly from the start instead
of trying to derive it later using count and offsetof.
Signed-off-by: David Teigland <teigland@redhat.com>
diff --git a/fs/dlm/user.c b/fs/dlm/user.c
index 065149e..ebce994 100644
--- a/fs/dlm/user.c
+++ b/fs/dlm/user.c
@@ -1,5 +1,5 @@
/*
- * Copyright (C) 2006-2008 Red Hat, Inc. All rights reserved.
+ * Copyright (C) 2006-2009 Red Hat, Inc. All rights reserved.
*
* This copyrighted material is made available to anyone wishing to use,
* modify, copy, or redistribute it subject to the terms and conditions
@@ -84,7 +84,7 @@
static void compat_input(struct dlm_write_request *kb,
struct dlm_write_request32 *kb32,
- size_t count)
+ int namelen)
{
kb->version[0] = kb32->version[0];
kb->version[1] = kb32->version[1];
@@ -96,8 +96,7 @@
kb->cmd == DLM_USER_REMOVE_LOCKSPACE) {
kb->i.lspace.flags = kb32->i.lspace.flags;
kb->i.lspace.minor = kb32->i.lspace.minor;
- memcpy(kb->i.lspace.name, kb32->i.lspace.name, count -
- offsetof(struct dlm_write_request32, i.lspace.name));
+ memcpy(kb->i.lspace.name, kb32->i.lspace.name, namelen);
} else if (kb->cmd == DLM_USER_PURGE) {
kb->i.purge.nodeid = kb32->i.purge.nodeid;
kb->i.purge.pid = kb32->i.purge.pid;
@@ -115,8 +114,7 @@
kb->i.lock.bastaddr = (void *)(long)kb32->i.lock.bastaddr;
kb->i.lock.lksb = (void *)(long)kb32->i.lock.lksb;
memcpy(kb->i.lock.lvb, kb32->i.lock.lvb, DLM_USER_LVB_LEN);
- memcpy(kb->i.lock.name, kb32->i.lock.name, count -
- offsetof(struct dlm_write_request32, i.lock.name));
+ memcpy(kb->i.lock.name, kb32->i.lock.name, namelen);
}
}
@@ -539,9 +537,16 @@
#ifdef CONFIG_COMPAT
if (!kbuf->is64bit) {
struct dlm_write_request32 *k32buf;
+ int namelen = 0;
+
+ if (count > sizeof(struct dlm_write_request32))
+ namelen = count - sizeof(struct dlm_write_request32);
+
k32buf = (struct dlm_write_request32 *)kbuf;
- kbuf = kmalloc(count + 1 + (sizeof(struct dlm_write_request) -
- sizeof(struct dlm_write_request32)), GFP_KERNEL);
+
+ /* add 1 after namelen so that the name string is terminated */
+ kbuf = kzalloc(sizeof(struct dlm_write_request) + namelen + 1,
+ GFP_KERNEL);
if (!kbuf) {
kfree(k32buf);
return -ENOMEM;
@@ -549,7 +554,8 @@
if (proc)
set_bit(DLM_PROC_FLAGS_COMPAT, &proc->flags);
- compat_input(kbuf, k32buf, count + 1);
+
+ compat_input(kbuf, k32buf, namelen);
kfree(k32buf);
}
#endif