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Commit a164009f authored by Jiri Slaby's avatar Jiri Slaby Committed by Greg Kroah-Hartman
Browse files

futex: futex_wake_op, fix sign_extend32 sign bits 



commit d70ef22892ed6c066e51e118b225923c9b74af34 upstream.

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 30d6e0a4190d ("futex: Remove duplicated code and fix undefined
behaviour") till now.

Fixes: 30d6e0a4190d ("futex: Remove duplicated code and fix undefined behaviour")
Signed-off-by: default avatarJiri 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: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 6f1abf86

kernel/futex.c

+2 −2
Original line number Diff line number Diff line
@@ -1462,8 +1462,8 @@ 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)) {