Commit dfb36e4a authored by Waiman Long's avatar Waiman Long Committed by Thomas Gleixner
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futex: Use user_write_access_begin/_end() in futex_put_value() 



Commit cec199c5 ("futex: Implement FUTEX2_NUMA") introduced the
futex_put_value() helper to write a value to the given user
address.

However, it uses user_read_access_begin() before the write. For
architectures that differentiate between read and write accesses, like
PowerPC, futex_put_value() fails with -EFAULT.

Fix that by using the user_write_access_begin/user_write_access_end() pair
instead.

Fixes: cec199c5 ("futex: Implement FUTEX2_NUMA")
Signed-off-by: default avatarWaiman Long <longman@redhat.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/20250811141147.322261-1-longman@redhat.com
parent e703b7e2

kernel/futex/futex.h

+3 −3
Original line number Diff line number Diff line
@@ -319,13 +319,13 @@ static __always_inline int futex_put_value(u32 val, u32 __user *to) 
{

	if (can_do_masked_user_access())

		to = masked_user_access_begin(to);

	else if (!user_read_access_begin(to, sizeof(*to)))

	else if (!user_write_access_begin(to, sizeof(*to)))

		return -EFAULT;

	unsafe_put_user(val, to, Efault);

	user_read_access_end();

	user_write_access_end();

	return 0;

Efault:

	user_read_access_end();

	user_write_access_end();

	return -EFAULT;

}