Re: [PATCH v6 01/10] file: Export receive_fd() to modules
From: Christian Brauner <hidden>
Date: 2021-03-31 09:16:40
Also in:
kvm, linux-fsdevel
Subsystem:
android drivers, the rest, tty layer and serial drivers · Maintainers:
Greg Kroah-Hartman, Arve Hjønnevåg, Todd Kjos, Christian Brauner, Carlos Llamas, Alice Ryhl, Linus Torvalds, Jiri Slaby
On Wed, Mar 31, 2021 at 04:05:10PM +0800, Xie Yongji wrote:
Export receive_fd() so that some modules can use it to pass file descriptor between processes without missing any security stuffs. Signed-off-by: Xie Yongji <redacted> ---
Yeah, as I said in the other mail I'd be comfortable with exposing just this variant of the helper. Maybe this should be a separate patch bundled together with Christoph's patch to split parts of receive_fd() into a separate helper. This would also allow us to simplify a few other codepaths in drivers as well btw. I just took a hasty stab at two of them:
diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index c119736ca56a..3c716bf6d84b 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c@@ -3728,8 +3728,9 @@ static int binder_apply_fd_fixups(struct binder_proc *proc, int ret = 0; list_for_each_entry(fixup, &t->fd_fixups, fixup_entry) { - int fd = get_unused_fd_flags(O_CLOEXEC); + int fd = receive_fd(fixup->file, O_CLOEXEC); + fd = receive_fd(fixup->file, O_CLOEXEC); if (fd < 0) { binder_debug(BINDER_DEBUG_TRANSACTION, "failed fd fixup txn %d fd %d\n",
@@ -3741,7 +3742,7 @@ static int binder_apply_fd_fixups(struct binder_proc *proc, "fd fixup txn %d fd %d\n", t->debug_id, fd); trace_binder_transaction_fd_recv(t, fd, fixup->offset); - fd_install(fd, fixup->file); + fput(fixup->file); fixup->file = NULL; if (binder_alloc_copy_to_buffer(&proc->alloc, t->buffer, fixup->offset, &fd,
diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index 5e2374580e27..c3a6b6abb7f4 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c@@ -629,12 +629,6 @@ int ptm_open_peer(struct file *master, struct tty_struct *tty, int flags) if (tty->driver != ptm_driver) return -EIO; - fd = get_unused_fd_flags(flags); - if (fd < 0) { - retval = fd; - goto err; - } - /* Compute the slave's path */ path.mnt = devpts_mntget(master, tty->driver_data); if (IS_ERR(path.mnt)) {
@@ -650,7 +644,8 @@ int ptm_open_peer(struct file *master, struct tty_struct *tty, int flags) goto err_put; } - fd_install(fd, filp); + fd = receive_fd(filp, flags); + fput(filp); return fd; err_put:
quoted hunk ↗ jump to hunk
fs/file.c | 6 ++++++ include/linux/file.h | 7 +++---- 2 files changed, 9 insertions(+), 4 deletions(-)diff --git a/fs/file.c b/fs/file.c index dab120b71e44..d7d957217576 100644 --- a/fs/file.c +++ b/fs/file.c@@ -1108,6 +1108,12 @@ int __receive_fd(int fd, struct file *file, int __user *ufd, unsigned int o_flag return new_fd; } +int receive_fd(struct file *file, unsigned int o_flags) +{ + return __receive_fd(-1, file, NULL, o_flags); +} +EXPORT_SYMBOL(receive_fd); + static int ksys_dup3(unsigned int oldfd, unsigned int newfd, int flags) { int err = -EBADF;diff --git a/include/linux/file.h b/include/linux/file.h index 225982792fa2..4667f9567d3e 100644 --- a/include/linux/file.h +++ b/include/linux/file.h@@ -94,6 +94,9 @@ extern void fd_install(unsigned int fd, struct file *file); extern int __receive_fd(int fd, struct file *file, int __user *ufd, unsigned int o_flags); + +extern int receive_fd(struct file *file, unsigned int o_flags); + static inline int receive_fd_user(struct file *file, int __user *ufd, unsigned int o_flags) {@@ -101,10 +104,6 @@ static inline int receive_fd_user(struct file *file, int __user *ufd, return -EFAULT; return __receive_fd(-1, file, ufd, o_flags); } -static inline int receive_fd(struct file *file, unsigned int o_flags) -{ - return __receive_fd(-1, file, NULL, o_flags); -} static inline int receive_fd_replace(int fd, struct file *file, unsigned int o_flags) { return __receive_fd(fd, file, NULL, o_flags);-- 2.11.0