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SubjectRe: New Defects based on recent changes in Kernel code found by Coverity Scan
On Thu, 5 Jul 2012 11:33:16 -0400 Chris Mason <chris.mason@fusionio.com> wrote:

> > > * CID 709112: Dereference after null check - fs/btrfs/ioctl.c, line: 1309 Comparing "device->fs_devices" to null implies that "device->fs_devices" might be null, and then it is deference
> > > fs/btrfs/ioctl.c:1309
> >
> > Chris.
>
> Thanks for forwarding this. But I'm a little confused, our line 1309 is
> this:
>
> if (device->fs_devices && device->fs_devices->seeding) {
>
> Is coverity telling me that I'm using fs_devices later on in the
> function without extra checks? Some functions we call do assume it
> isn't null, but the seeding devices are special snowflakes.

There were more details further down in the email:

> ____________________________________________________________________________________________________________
> CID 709112: Dereference after null check
>
> fs/btrfs/ioctl.c:1309
> 1256 static noinline int btrfs_ioctl_resize(struct btrfs_root *root,
> 1257 void __user *arg)
> 1258 {
> ...
> >>> At conditional (1): "device->fs_devices" taking the false branch.
> >>> CID 709112: Dereference after null check (FORWARD_NULL) Comparing "device->fs_devices" to null implies that "device->fs_devices" might be null.
> 1309 if (device->fs_devices && device->fs_devices->seeding) {
> 1310 printk(KERN_INFO "btrfs: resizer unable to apply on "
> 1311 "seeding device %llu\n", devid);
> 1312 ret = -EINVAL;
> 1313 goto out_free;
> 1314 }
> ...
> >>> Passing null variable "device->fs_devices" to function "btrfs_grow_device", which dereferences it.
> 1367 ret = btrfs_grow_device(trans, device, new_size);
> 1368 btrfs_commit_transaction(trans, root);
> 1369 } else if (new_size < old_size) {
> >>> Passing null variable "device->fs_devices" to function "btrfs_shrink_device", which dereferences it.
> 1370 ret = btrfs_shrink_device(device, new_size);
> 1371 }
> 1378 }


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