[PATCH v2 01/10] iter: Avoid barrier_nospec() in copy_from_user_iter()
From: Christophe Leroy <hidden>
Date: 2025-08-22 10:20:44
Also in:
linux-fsdevel, linux-mm, linuxppc-dev, lkml
Subsystem:
library code, the rest, userspace copyin/copyout (uiovec) · Maintainers:
Andrew Morton, Linus Torvalds, Alexander Viro
Following patch will add missing barrier_nospec() to
copy_from_user_iter().
Avoid it for architectures supporting masked user
accesses, the same way as done for copy_from_user() by
commit 0fc810ae3ae1 ("x86/uaccess: Avoid barrier_nospec()
in 64-bit copy_from_user()")
Signed-off-by: Christophe Leroy <redacted>
---
v2: New in v2
---
lib/iov_iter.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index f9193f952f49..48bd0cbce8c2 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c@@ -49,12 +49,16 @@ size_t copy_from_user_iter(void __user *iter_from, size_t progress, if (should_fail_usercopy()) return len; - if (access_ok(iter_from, len)) { - to += progress; - instrument_copy_from_user_before(to, iter_from, len); - res = raw_copy_from_user(to, iter_from, len); - instrument_copy_from_user_after(to, iter_from, len, res); - } + if (can_do_masked_user_access()) + iter_from = mask_user_address(iter_from); + else if (!access_ok(iter_from, len)) + return res; + + to += progress; + instrument_copy_from_user_before(to, iter_from, len); + res = raw_copy_from_user(to, iter_from, len); + instrument_copy_from_user_after(to, iter_from, len, res); + return res; }
--
2.49.0