From 32913f348229c9f72dda45fc2c08c6d9dfcd3d6d Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Mon, 9 Dec 2024 10:00:25 -0800 Subject: [PATCH] futex: fix user access on powerpc The powerpc user access code is special, and unlike other architectures distinguishes between user access for reading and writing. And commit 43a43faf5376 ("futex: improve user space accesses") messed that up. It went undetected elsewhere, but caused ppc32 to fail early during boot, because the user access had been started with user_read_access_begin(), but then finished off with just a plain "user_access_end()". Note that the address-masking user access helpers don't even have that read-vs-write distinction, so if powerpc ever wants to do address masking tricks, we'll have to do some extra work for it. [ Make sure to also do it for the EFAULT case, as pointed out by Christophe Leroy ] Reported-by: Andreas Schwab Cc: Christophe Leroy Link: https://lore.kernel.org/all/87bjxl6b0i.fsf@igel.home/ Signed-off-by: Linus Torvalds --- kernel/futex/futex.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/futex/futex.h b/kernel/futex/futex.h index 618ce1fe870e..99b32e728c4a 100644 --- a/kernel/futex/futex.h +++ b/kernel/futex/futex.h @@ -265,11 +265,11 @@ static __always_inline int futex_read_inatomic(u32 *dest, u32 __user *from) else if (!user_read_access_begin(from, sizeof(*from))) return -EFAULT; unsafe_get_user(val, from, Efault); - user_access_end(); + user_read_access_end(); *dest = val; return 0; Efault: - user_access_end(); + user_read_access_end(); return -EFAULT; }