Commit 5e307a6b authored Jul 17, 2019 by Josh Poimboeuf Committed by Thomas Gleixner Jul 18, 2019

x86/uaccess: Don't leak AC flag into fentry from mcsafe_handle_tail()

After adding mcsafe_handle_tail() to the objtool uaccess safe list,
objtool reports:

arch/x86/lib/usercopy_64.o: warning: objtool: mcsafe_handle_tail()+0x0: call to __fentry__() with UACCESS enabled

With SMAP, this function is called with AC=1, so it needs to be careful
about which functions it calls. Disable the ftrace entry hook, which
can potentially pull in a lot of extra code.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/8e13d6f0da1c8a3f7603903da6cbf6d582bbfe10.1563413318.git.jpoimboe@redhat.com

parent 3a6ab4bc

arch/x86/lib/usercopy_64.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -60,7 +60,7 @@ EXPORT_SYMBOL(clear_user);
		* but reuse __memcpy_mcsafe in case a new read error is encountered.
		* clac() is handled in _copy_to_iter_mcsafe().
		*/
		__visible unsigned long
		__visible notrace unsigned long
		mcsafe_handle_tail(char to, char from, unsigned len)
		{
		for (; len; --len, to++, from++) {