5.10-stable review patch. If anyone has any objections, please let me know.
------------------
From: Thomas Weißschuh thomas.weissschuh@linutronix.de
commit 708c04a5c2b78e22f56e2350de41feba74dfccd9 upstream.
replace_fd() returns the number of the new file descriptor through the return value of do_dup2(). However its callers never care about the specific returned number. In fact the caller in receive_fd_replace() treats any non-zero return value as an error and therefore never calls __receive_sock() for most file descriptors, which is a bug.
To fix the bug in receive_fd_replace() and to avoid the same issue happening in future callers, signal success through a plain zero.
Suggested-by: Al Viro viro@zeniv.linux.org.uk Link: https://lore.kernel.org/lkml/20250801220215.GS222315@ZenIV/ Fixes: 173817151b15 ("fs: Expand __receive_fd() to accept existing fd") Fixes: 42eb0d54c08a ("fs: split receive_fd_replace from __receive_fd") Cc: stable@vger.kernel.org Signed-off-by: Thomas Weißschuh thomas.weissschuh@linutronix.de Link: https://lore.kernel.org/20250805-fix-receive_fd_replace-v3-1-b72ba8b34bac@li... Signed-off-by: Christian Brauner brauner@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/file.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
--- a/fs/file.c +++ b/fs/file.c @@ -1095,7 +1095,10 @@ int replace_fd(unsigned fd, struct file err = expand_files(files, fd); if (unlikely(err < 0)) goto out_unlock; - return do_dup2(files, file, fd, flags); + err = do_dup2(files, file, fd, flags); + if (err < 0) + return err; + return 0;
out_unlock: spin_unlock(&files->file_lock);