Commit d70ef228 authored Nov 30, 2017 by Jiri Slaby Committed by Linus Torvalds Dec 10, 2017

futex: futex_wake_op, fix sign_extend32 sign bits



sign_extend32 counts the sign bit parameter from 0, not from 1.  So we
have to use "11" for 12th bit, not "12".

This mistake means we have not allowed negative op and cmp args since
commit 30d6e0a4 ("futex: Remove duplicated code and fix undefined
behaviour") till now.

Fixes: 30d6e0a4 ("futex: Remove duplicated code and fix undefined behaviour")
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Darren Hart <dvhart@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 51090c5d

kernel/futex.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -1582,8 +1582,8 @@ static int futex_atomic_op_inuser(unsigned int encoded_op, u32 __user *uaddr)
		{
		unsigned int op = (encoded_op & 0x70000000) >> 28;
		unsigned int cmp = (encoded_op & 0x0f000000) >> 24;
		int oparg = sign_extend32((encoded_op & 0x00fff000) >> 12, 12);
		int cmparg = sign_extend32(encoded_op & 0x00000fff, 12);
		int oparg = sign_extend32((encoded_op & 0x00fff000) >> 12, 11);
		int cmparg = sign_extend32(encoded_op & 0x00000fff, 11);
		int oldval, ret;

		if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28)) {

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