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dlm: fix length calculation in compat code

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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>
This commit is contained in:
David Teigland 2009-03-04 11:17:23 -06:00
parent a536e38125
commit 1fecb1c4b6
1 changed files with 15 additions and 9 deletions
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24
fs/dlm/user.c
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@ -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 @@ struct dlm_lock_result32 {
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 @@ static void compat_input(struct dlm_write_request *kb,
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 @@ static void compat_input(struct dlm_write_request *kb,
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 @@ static ssize_t device_write(struct file *file, const char __user *buf,
#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 @@ static ssize_t device_write(struct file *file, const char __user *buf,
if (proc)
set_bit(DLM_PROC_FLAGS_COMPAT, &proc->flags);
compat_input(kbuf, k32buf, count + 1);
compat_input(kbuf, k32buf, namelen);
kfree(k32buf);
}
#endif