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authorMathias Krause <minipli@grsecurity.net>2022-02-07 16:01:19 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2022-02-11 12:13:22 +0100
commitc72ea20503610a4a7ba26c769357d31602769c01 (patch)
tree062ddea6ce0e4f227e8d69025a2b21b6b88972a7 /drivers
parentbca828ccdd6548d24613d0cede04ada4dfb2f89c (diff)
iio: buffer: Fix file related error handling in IIO_BUFFER_GET_FD_IOCTL
If we fail to copy the just created file descriptor to userland, we try to clean up by putting back 'fd' and freeing 'ib'. The code uses put_unused_fd() for the former which is wrong, as the file descriptor was already published by fd_install() which gets called internally by anon_inode_getfd(). This makes the error handling code leaving a half cleaned up file descriptor table around and a partially destructed 'file' object, allowing userland to play use-after-free tricks on us, by abusing the still usable fd and making the code operate on a dangling 'file->private_data' pointer. Instead of leaving the kernel in a partially corrupted state, don't attempt to explicitly clean up and leave this to the process exit path that'll release any still valid fds, including the one created by the previous call to anon_inode_getfd(). Simply return -EFAULT to indicate the error. Fixes: f73f7f4da581 ("iio: buffer: add ioctl() to support opening extra buffers for IIO device") Cc: stable@kernel.org Cc: Jonathan Cameron <jic23@kernel.org> Cc: Alexandru Ardelean <ardeleanalex@gmail.com> Cc: Lars-Peter Clausen <lars@metafoo.de> Cc: Nuno Sa <Nuno.Sa@analog.com> Reported-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Mathias Krause <minipli@grsecurity.net> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/iio/industrialio-buffer.c14
1 files changed, 11 insertions, 3 deletions
diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
index 94eb9f6cf128..208b5193c621 100644
--- a/drivers/iio/industrialio-buffer.c
+++ b/drivers/iio/industrialio-buffer.c
@@ -1569,9 +1569,17 @@ static long iio_device_buffer_getfd(struct iio_dev *indio_dev, unsigned long arg
}
if (copy_to_user(ival, &fd, sizeof(fd))) {
- put_unused_fd(fd);
- ret = -EFAULT;
- goto error_free_ib;
+ /*
+ * "Leak" the fd, as there's not much we can do about this
+ * anyway. 'fd' might have been closed already, as
+ * anon_inode_getfd() called fd_install() on it, which made
+ * it reachable by userland.
+ *
+ * Instead of allowing a malicious user to play tricks with
+ * us, rely on the process exit path to do any necessary
+ * cleanup, as in releasing the file, if still needed.
+ */
+ return -EFAULT;
}
return 0;