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SubjectRe: [PATCH 2.4] i2c-dev user/kernel bug and mem leak
From
Date
On Fri, 2003-08-15 at 14:13, Greg KH wrote:
> Hm, I had already applied your patch, so this one doesn't apply. Care
> to re-do it against 2.6.0-test4 whenever that comes out?

Here's the patch against 2.6.0-test4. Just to remind everyone, this
patch doesn't fix any bugs (they're already fixed in 2.6.0-test3), it
just makes the code pass our static analysis tool, cqual, without
generating a warning. Since finding and fixing these bugs is so tricky,
it seems worthwhile to have code which can be automatically verified to
be bug-free (at least w.r.t. user/kernel pointers). That's what this
patch is about. Let me know if you have any questions or comments.
Thanks for everyone's help.

Best,
Rob

P.S. cqual is on its way -- we're working on documentation and
integrating it into the kernel build process.


--- drivers/i2c/i2c-dev.c.orig Wed Aug 27 18:04:31 2003
+++ drivers/i2c/i2c-dev.c Wed Aug 27 17:51:23 2003
@@ -181,7 +181,7 @@
struct i2c_smbus_ioctl_data data_arg;
union i2c_smbus_data temp;
struct i2c_msg *rdwr_pa;
- u8 **data_ptrs;
+ struct i2c_msg *tmp_pa;
int i,datasize,res;
unsigned long funcs;

@@ -226,40 +226,44 @@
if (rdwr_arg.nmsgs > 42)
return -EINVAL;

- rdwr_pa = (struct i2c_msg *)
+ tmp_pa = (struct i2c_msg *)
kmalloc(rdwr_arg.nmsgs * sizeof(struct i2c_msg),
GFP_KERNEL);

- if (rdwr_pa == NULL) return -ENOMEM;
+ if (tmp_pa == NULL) return -ENOMEM;

- if (copy_from_user(rdwr_pa, rdwr_arg.msgs,
+ if (copy_from_user(tmp_pa, rdwr_arg.msgs,
rdwr_arg.nmsgs * sizeof(struct i2c_msg))) {
- kfree(rdwr_pa);
+ kfree(tmp_pa);
return -EFAULT;
}

- data_ptrs = (u8 **) kmalloc(rdwr_arg.nmsgs * sizeof(u8 *),
- GFP_KERNEL);
- if (data_ptrs == NULL) {
- kfree(rdwr_pa);
+ rdwr_pa = (struct i2c_msg *)
+ kmalloc(rdwr_arg.nmsgs * sizeof(struct i2c_msg),
+ GFP_KERNEL);
+
+ if (rdwr_pa == NULL) {
+ kfree(tmp_pa);
return -ENOMEM;
}

res = 0;
for( i=0; i<rdwr_arg.nmsgs; i++ ) {
+ rdwr_pa[i].addr = tmp_pa[i].addr;
+ rdwr_pa[i].flags = tmp_pa[i].flags;
+ rdwr_pa[i].len = tmp_pa[i].len;
/* Limit the size of the message to a sane amount */
if (rdwr_pa[i].len > 8192) {
res = -EINVAL;
break;
}
- data_ptrs[i] = rdwr_pa[i].buf;
rdwr_pa[i].buf = kmalloc(rdwr_pa[i].len, GFP_KERNEL);
if(rdwr_pa[i].buf == NULL) {
res = -ENOMEM;
break;
}
if(copy_from_user(rdwr_pa[i].buf,
- data_ptrs[i],
+ tmp_pa[i].buf,
rdwr_pa[i].len)) {
++i; /* Needs to be kfreed too */
res = -EFAULT;
@@ -270,8 +274,8 @@
int j;
for (j = 0; j < i; ++j)
kfree(rdwr_pa[j].buf);
- kfree(data_ptrs);
kfree(rdwr_pa);
+ kfree(tmp_pa);
return res;
}

@@ -281,7 +285,7 @@
while(i-- > 0) {
if( res>=0 && (rdwr_pa[i].flags & I2C_M_RD)) {
if(copy_to_user(
- data_ptrs[i],
+ tmp_pa[i].buf,
rdwr_pa[i].buf,
rdwr_pa[i].len)) {
res = -EFAULT;
@@ -289,8 +293,8 @@
}
kfree(rdwr_pa[i].buf);
}
- kfree(data_ptrs);
kfree(rdwr_pa);
+ kfree(tmp_pa);
return res;

case I2C_SMBUS:
-
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