From 1dc88208cfdce26858c59609242f2bb0e2b5c031 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Fri, 10 Jul 2026 11:33:07 +0200 Subject: [PATCH] binfmt_misc: annotate racy accesses to ->enabled ->enabled has always been read and written locklessly: every exec reads it in load_misc_binary() while bm_status_write() or a concurrent remount via bm_fill_super() may flip it. That is fine as it is an independent boolean toggle but the accesses should be marked accordingly for KCSAN. Annotate them with READ_ONCE()/WRITE_ONCE(). Link: https://patch.msgid.link/20260710-work-binfmt_misc-locking-v3-6-a162f7cb58d6@kernel.org Reviewed-by: Jori Koolstra Signed-off-by: Christian Brauner (Amutable) --- fs/binfmt_misc.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c index 236ebaf3be5c..0e56eb225862 100644 --- a/fs/binfmt_misc.c +++ b/fs/binfmt_misc.c @@ -217,7 +217,7 @@ static int load_misc_binary(struct linux_binprm *bprm) struct binfmt_misc *misc; misc = load_binfmt_misc(); - if (!misc->enabled) + if (!READ_ONCE(misc->enabled)) return retval; fmt = get_binfmt_handler(misc, bprm); @@ -874,7 +874,7 @@ bm_status_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos) char *s; misc = i_binfmt_misc(file_inode(file)); - s = misc->enabled ? "enabled\n" : "disabled\n"; + s = READ_ONCE(misc->enabled) ? "enabled\n" : "disabled\n"; return simple_read_from_buffer(buf, nbytes, ppos, s, strlen(s)); } @@ -891,11 +891,11 @@ static ssize_t bm_status_write(struct file *file, const char __user *buffer, switch (res) { case 1: /* Disable all handlers. */ - misc->enabled = false; + WRITE_ONCE(misc->enabled, false); break; case 2: /* Enable all handlers. */ - misc->enabled = true; + WRITE_ONCE(misc->enabled, true); break; case 3: /* Delete all handlers. */ @@ -1000,7 +1000,7 @@ static int bm_fill_super(struct super_block *sb, struct fs_context *fc) * is true. Instead, if someone mounts binfmt_misc for the first time or * again we simply reset ->enabled to true. */ - misc->enabled = true; + WRITE_ONCE(misc->enabled, true); err = simple_fill_super(sb, BINFMTFS_MAGIC, bm_files); if (!err)