From 882c6f260d19d4a173d735bac3568af00294ed51 Mon Sep 17 00:00:00 2001 From: Alexander Potapenko Date: Mon, 24 Oct 2022 23:21:43 +0200 Subject: [PATCH] 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: 3420bb532956 ("x86: asm: instrument usercopy in get_user() and put_user()") Signed-off-by: Alexander Potapenko Reported-by: youling257 Cc: Borislav Petkov Cc: Ingo Molnar Cc: Thomas Gleixner Signed-off-by: Andrew Morton --- arch/x86/include/asm/uaccess.h | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h index 8bc614cfe21b9..1cc756eafa447 100644 --- a/arch/x86/include/asm/uaccess.h +++ b/arch/x86/include/asm/uaccess.h @@ -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 -- 2.39.5