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binfmt_misc: annotate racy accesses to ->enabled

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->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 <jkoolstra@xs4all.nl>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
This commit is contained in:
Christian Brauner
2026-07-10 11:33:07 +02:00
parent fd77da3efb
commit 1dc88208cf
1 changed files with 5 additions and 5 deletions
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10
fs/binfmt_misc.c
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@@ -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)