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futex: Use user_write_access_begin/_end() in futex_put_value()

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commit dfb36e4a8d upstream.

Commit cec199c5e3 ("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: cec199c5e3 ("futex: Implement FUTEX2_NUMA")
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/20250811141147.322261-1-longman@redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Waiman Long 2025-08-11 10:11:47 -04:00 committed by Greg Kroah-Hartman
parent f43a9420e1
commit 6b3942f8b0
1 changed files with 3 additions and 3 deletions
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6
kernel/futex/futex.h
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@ -321,13 +321,13 @@ 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;
}