Commit 59c8a02e authored Oct 24, 2022 by Alexander Potapenko Committed by Andrew Morton Oct 28, 2022

x86: asm: make sure __put_user_size() evaluates pointer once

User access macros must ensure their arguments are evaluated only once if
they are used more than once in the macro body.  Adding
instrument_put_user() to __put_user_size() resulted in double evaluation
of the `ptr` argument, which led to correctness issues when performing
e.g.  unsafe_put_user(..., p++, ...).

To fix those issues, evaluate the `ptr` argument of __put_user_size() at
the beginning of the macro.

Link: https://lkml.kernel.org/r/20221024212144.2852069-4-glider@google.com


Fixes: 888f84a6 ("x86: asm: instrument usercopy in get_user() and put_user()")
Signed-off-by: Alexander Potapenko <glider@google.com>
Reported-by: youling257 <youling257@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

parent 921757bc

arch/x86/include/asm/uaccess.h

+7 −6

Original line number	Diff line number	Diff line
		@@ -254,24 +254,25 @@ extern void __put_user_nocheck_8(void);
		#define __put_user_size(x, ptr, size, label) \
		do { \
		__typeof__((ptr)) __x = (x); / eval x once */ \
		__chk_user_ptr(ptr); \
		__typeof__(ptr) __ptr = (ptr); /* eval ptr once */ \
		__chk_user_ptr(__ptr); \
		switch (size) { \
		case 1: \
		__put_user_goto(__x, ptr, "b", "iq", label); \
		__put_user_goto(__x, __ptr, "b", "iq", label); \
		break; \
		case 2: \
		__put_user_goto(__x, ptr, "w", "ir", label); \
		__put_user_goto(__x, __ptr, "w", "ir", label); \
		break; \
		case 4: \
		__put_user_goto(__x, ptr, "l", "ir", label); \
		__put_user_goto(__x, __ptr, "l", "ir", label); \
		break; \
		case 8: \
		__put_user_goto_u64(__x, ptr, label); \
		__put_user_goto_u64(__x, __ptr, label); \
		break; \
		default: \
		__put_user_bad(); \
		} \
		instrument_put_user(__x, ptr, size); \
		instrument_put_user(__x, __ptr, size); \
		} while (0)

		#ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT