From 52d0b8b18776f184c53632c5e0068201491cdb61 Mon Sep 17 00:00:00 2001 From: Marco Elver Date: Fri, 26 Nov 2021 13:47:46 +0100 Subject: x86/fpu/signal: Initialize sw_bytes in save_xstate_epilog() save_sw_bytes() did not fully initialize sw_bytes, which caused KMSAN to report an infoleak (see below). Initialize sw_bytes explicitly to avoid this. KMSAN report follows: ===================================================== BUG: KMSAN: kernel-infoleak in instrument_copy_to_user ./include/linux/instrumented.h:121 BUG: KMSAN: kernel-infoleak in __copy_to_user ./include/linux/uaccess.h:154 BUG: KMSAN: kernel-infoleak in save_xstate_epilog+0x2df/0x510 arch/x86/kernel/fpu/signal.c:127 instrument_copy_to_user ./include/linux/instrumented.h:121 __copy_to_user ./include/linux/uaccess.h:154 save_xstate_epilog+0x2df/0x510 arch/x86/kernel/fpu/signal.c:127 copy_fpstate_to_sigframe+0x861/0xb60 arch/x86/kernel/fpu/signal.c:245 get_sigframe+0x656/0x7e0 arch/x86/kernel/signal.c:296 __setup_rt_frame+0x14d/0x2a60 arch/x86/kernel/signal.c:471 setup_rt_frame arch/x86/kernel/signal.c:781 handle_signal arch/x86/kernel/signal.c:825 arch_do_signal_or_restart+0x417/0xdd0 arch/x86/kernel/signal.c:870 handle_signal_work kernel/entry/common.c:149 exit_to_user_mode_loop+0x1f6/0x490 kernel/entry/common.c:173 exit_to_user_mode_prepare kernel/entry/common.c:208 __syscall_exit_to_user_mode_work kernel/entry/common.c:290 syscall_exit_to_user_mode+0x7e/0xc0 kernel/entry/common.c:302 do_syscall_64+0x60/0xd0 arch/x86/entry/common.c:88 entry_SYSCALL_64_after_hwframe+0x44/0xae ??:? Local variable sw_bytes created at: save_xstate_epilog+0x80/0x510 arch/x86/kernel/fpu/signal.c:121 copy_fpstate_to_sigframe+0x861/0xb60 arch/x86/kernel/fpu/signal.c:245 Bytes 20-47 of 48 are uninitialized Memory access of size 48 starts at ffff8880801d3a18 Data copied to user address 00007ffd90e2ef50 ===================================================== Link: https://lore.kernel.org/all/CAG_fn=V9T6OKPonSjsi9PmWB0hMHFC=yawozdft8i1-MSxrv=w@mail.gmail.com/ Fixes: 53599b4d54b9b8dd ("x86/fpu/signal: Prepare for variable sigframe length") Reported-by: Alexander Potapenko Signed-off-by: Marco Elver Signed-off-by: Alexander Potapenko Signed-off-by: Dave Hansen Tested-by: Alexander Potapenko Link: https://lkml.kernel.org/r/20211126124746.761278-1-glider@google.com --- arch/x86/kernel/fpu/signal.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch') diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c index d5958278eba6..91d4b6de58ab 100644 --- a/arch/x86/kernel/fpu/signal.c +++ b/arch/x86/kernel/fpu/signal.c @@ -118,7 +118,7 @@ static inline bool save_xstate_epilog(void __user *buf, int ia32_frame, struct fpstate *fpstate) { struct xregs_state __user *x = buf; - struct _fpx_sw_bytes sw_bytes; + struct _fpx_sw_bytes sw_bytes = {}; u32 xfeatures; int err; -- cgit v1.2.3