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.wong@xxxxxxxxxx>
---
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)
--
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