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authorKees Cook <keescook@chromium.org>2020-06-10 08:46:58 -0700
committerKees Cook <keescook@chromium.org>2020-07-13 11:03:45 -0700
commit173817151b15d5a72a9bef1d2df7e6e7f6750f2e (patch)
tree16375b677a419dd9405ec53183315afc85e25c1e /fs/file.c
parent910d2f16ac90463a1f5b03d53246c443e2b354b9 (diff)
fs: Expand __receive_fd() to accept existing fd
Expand __receive_fd() with support for replace_fd() for the coming seccomp "addfd" ioctl(). Add new wrapper receive_fd_replace() for the new behavior and update existing wrappers to retain old behavior. Thanks to Colin Ian King <colin.king@canonical.com> for pointing out an uninitialized variable exposure in an earlier version of this patch. Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Dmitry Kadashev <dkadashev@gmail.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Arnd Bergmann <arnd@arndb.de> Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Sargun Dhillon <sargun@sargun.me> Acked-by: Christian Brauner <christian.brauner@ubuntu.com> Signed-off-by: Kees Cook <keescook@chromium.org>
Diffstat (limited to 'fs/file.c')
-rw-r--r--fs/file.c25
1 files changed, 19 insertions, 6 deletions
diff --git a/fs/file.c b/fs/file.c
index 56d96d5c0c9f..4fb111735d1d 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -939,6 +939,7 @@ out_unlock:
/**
* __receive_fd() - Install received file into file descriptor table
*
+ * @fd: fd to install into (if negative, a new fd will be allocated)
* @file: struct file that was received from another process
* @ufd: __user pointer to write new fd number to
* @o_flags: the O_* flags to apply to the new fd entry
@@ -952,7 +953,7 @@ out_unlock:
*
* Returns newly install fd or -ve on error.
*/
-int __receive_fd(struct file *file, int __user *ufd, unsigned int o_flags)
+int __receive_fd(int fd, struct file *file, int __user *ufd, unsigned int o_flags)
{
int new_fd;
int error;
@@ -961,21 +962,33 @@ int __receive_fd(struct file *file, int __user *ufd, unsigned int o_flags)
if (error)
return error;
- new_fd = get_unused_fd_flags(o_flags);
- if (new_fd < 0)
- return new_fd;
+ if (fd < 0) {
+ new_fd = get_unused_fd_flags(o_flags);
+ if (new_fd < 0)
+ return new_fd;
+ } else {
+ new_fd = fd;
+ }
if (ufd) {
error = put_user(new_fd, ufd);
if (error) {
- put_unused_fd(new_fd);
+ if (fd < 0)
+ put_unused_fd(new_fd);
return error;
}
}
+ if (fd < 0) {
+ fd_install(new_fd, get_file(file));
+ } else {
+ error = replace_fd(new_fd, file, o_flags);
+ if (error)
+ return error;
+ }
+
/* Bump the sock usage counts, if any. */
__receive_sock(file);
- fd_install(new_fd, get_file(file));
return new_fd;
}