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pidfs: preserve thread pidfds reopened by file handle

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PIDFD_THREAD shares O_EXCL. do_dentry_open() clears O_EXCL after
pidfs_export_open() validates the flags, so open_by_handle_at()
silently turns a thread pidfd into a process pidfd.

Restore PIDFD_THREAD on the opened file, matching pidfs_alloc_file().

Signed-off-by: Li Chen <me@linux.beauty>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20260716052726.1032092-1-me@linux.beauty
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
This commit is contained in:
Christian Brauner 2026-07-22 13:50:53 +02:00
parent a8e72879cd
commit bb6bc13c53
1 changed files with 7 additions and 1 deletions
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8
fs/pidfs.c
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@ -939,12 +939,18 @@ static int pidfs_export_permission(struct handle_to_path_ctx *ctx,
static struct file *pidfs_export_open(const struct path *path, unsigned int oflags)
{
struct file *file;
/*
* Clear O_LARGEFILE as open_by_handle_at() forces it and raise
* O_RDWR as pidfds always are.
*/
oflags &= ~O_LARGEFILE;
return dentry_open(path, oflags | O_RDWR, current_cred());
file = dentry_open(path, oflags | O_RDWR, current_cred());
/* do_dentry_open() strips O_EXCL, which encodes PIDFD_THREAD. */
if (!IS_ERR(file))
file->f_flags |= oflags & PIDFD_THREAD;
return file;
}
static const struct export_operations pidfs_export_operations = {