On Fri, Dec 20, 2013 at 03:35:34PM -0800, Darrick J. Wong wrote:
> The IOC_[GS]ETFLAGS and IOC_[GS]ETVERSION ioctls, despite being
> defined to take a "long" parameter, actually take "int" parameters.
> FUSE unfortunately assumed that the ioctl definitions never lie, and
FUSE doesn't really assume anything. It just says, that ioctl's that *properly*
use the _IO* macros will work. Everything else will not.
It's unfortunate that IOC_SET/GETFLAGS is something that may actually make sense
on a fuse filesystem...
Two ways out of this:
A) Add quirks to fuse
B) Add new, fixed ioctls and use those from chattr if available
I'd very much prefer B.
Thanks,
Miklos
> transfers a long's worth of data in and out of userspace, which causes
> stack smashing in chattr, and other bugs elsewhere.
>
> So, special-case this in FUSE so that we don't crash userland.
>
> v2: Do the same for the IOC_[GS]ETVERSION ioctls, as Richard Hansen
> points out.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> ---
> fs/fuse/file.c | 16 ++++++++++++++++
> 1 file changed, 16 insertions(+)
>
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index 7e70506..f8766ab 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -2385,6 +2385,22 @@ long fuse_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg,
> iov->iov_base = (void __user *)arg;
> iov->iov_len = _IOC_SIZE(cmd);
>
> + /*
> + * The IOC_[GS]ETFLAGS and IOC_[GS]ETVERSION ioctls take int
> + * parameters even though the ioctl definition specifies long.
> + * Userland has been expecting int for ages (and chattr
> + * segfaults on FUSE filesystems), so special case that here.
> + * The IOC32 variants were declared with int, so they don't
> + * need this correction.
> + */
> + switch (cmd) {
> + case FS_IOC_GETFLAGS:
> + case FS_IOC_SETFLAGS:
> + case FS_IOC_GETVERSION:
> + case FS_IOC_SETVERSION:
> + iov->iov_len = sizeof(int);
> + }
> +
> if (_IOC_DIR(cmd) & _IOC_WRITE) {
> in_iov = iov;
> in_iovs = 1;
>
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