From: Christophe Leroy Date: Mon, 17 Nov 2025 16:43:42 +0000 (+0100) Subject: iov_iter: Add missing speculation barrier to copy_from_user_iter() X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=803abedbd540617f136a2c4d7066ff2e304f016d;p=thirdparty%2Flinux.git iov_iter: Add missing speculation barrier to copy_from_user_iter() The results of "access_ok()" can be mis-speculated. The result is that the CPU can end speculatively: if (access_ok(from, size)) // Right here For the same reason as done in copy_from_user() in commit 74e19ef0ff80 ("uaccess: Add speculation barrier to copy_from_user()"), add a speculation barrier to copy_from_user_iter(). Signed-off-by: Christophe Leroy Signed-off-by: Thomas Gleixner Link: https://patch.msgid.link/6b73e69cc7168c89df4eab0a216e3ed4cca36b0a.1763396724.git.christophe.leroy@csgroup.eu --- diff --git a/lib/iov_iter.c b/lib/iov_iter.c index a589935bf3025..896760bad455f 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -49,11 +49,19 @@ size_t copy_from_user_iter(void __user *iter_from, size_t progress, if (should_fail_usercopy()) return len; - if (can_do_masked_user_access()) + if (can_do_masked_user_access()) { iter_from = mask_user_address(iter_from); - else if (!access_ok(iter_from, len)) - return res; + } else { + if (!access_ok(iter_from, len)) + return res; + /* + * Ensure that bad access_ok() speculation will not + * lead to nasty side effects *after* the copy is + * finished: + */ + barrier_nospec(); + } to += progress; instrument_copy_from_user_before(to, iter_from, len); res = raw_copy_from_user(to, iter_from, len);