On 2013-12-19 18:27, Darrick J. Wong wrote:
> The IOC_[GS]ETFLAGS ioctls, despite being defined to take a "long"
> parameter, actually take "int" parameters. FUSE unfortunately assumed
> that the ioctl definitions never lie, and 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, and document this int/long quirk in
> include/uapi/linux/fs.h.
>
> Signed-off-by: Darrick J. Wong <darrick.w...@oracle.com>
> ---
> fs/fuse/file.c | 11 +++++++++++
> include/uapi/linux/fs.h | 1 +
> 2 files changed, 12 insertions(+)
>
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index 7e70506..5fa8181 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -2385,6 +2385,17 @@ 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 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.
> + */
> + if (cmd == FS_IOC_GETFLAGS || cmd == FS_IOC_SETFLAGS) {
> + iov->iov_len = sizeof(int);
> + }
> +
> if (_IOC_DIR(cmd) & _IOC_WRITE) {
> in_iov = iov;
> in_iovs = 1;
> diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
> index 6c28b61..bc8aa8e 100644
> --- a/include/uapi/linux/fs.h
> +++ b/include/uapi/linux/fs.h
> @@ -154,6 +154,7 @@ struct inodes_stat_t {
> #define FITHAW _IOWR('X', 120, int) /* Thaw */
> #define FITRIM _IOWR('X', 121, struct fstrim_range) /* Trim
> */
>
> +/* IOC_[GS]ETFLAGS take an int argument despite being defined to take long.
> */
> #define FS_IOC_GETFLAGS _IOR('f', 1, long)
> #define FS_IOC_SETFLAGS _IOW('f', 2, long)
> #define FS_IOC_GETVERSION _IOR('v', 1, long)
This change to include/uapi/linux/fs.h is similar to but not as thorough as:
http://mid.gmane.org/1385548839-16617-1-git-send-email-aurel...@aurel32.net
https://lkml.org/lkml/2013/11/27/93
(The above linked patch is the patch Aurelien referenced in the
"Argument type for FS_IOC_GETFLAGS/FS_IOC_SETFLAGS ioctls" thread on
linux-fsdevel; see
<http://mid.gmane.org/20131127231430.gg29...@hall.aurel32.net>.)
-Richard
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