From: Alexander Potapenko <glider@google.com>
To: tglx@linutronix.de, chang.seok.bae@intel.com, bp@suse.de
Cc: dvyukov@google.com, elver@google.com, x86@kernel.org,
linux-kernel@vger.kernel.org,
Alexander Potapenko <glider@google.com>
Subject: [PATCH] x86/fpu/signal: initialize sw_bytes in save_xstate_epilog()
Date: Fri, 26 Nov 2021 13:47:46 +0100 [thread overview]
Message-ID: <20211126124746.761278-1-glider@google.com> (raw)
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
=====================================================
Reported-by: Alexander Potapenko <glider@google.com>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Alexander Potapenko <glider@google.com>
Tested-by: Alexander Potapenko <glider@google.com>
Fixes: 53599b4d54b9b8dd ("x86/fpu/signal: Prepare for variable sigframe length")
Link: https://lore.kernel.org/all/CAG_fn=V9T6OKPonSjsi9PmWB0hMHFC=yawozdft8i1-MSxrv=w@mail.gmail.com/
---
arch/x86/kernel/fpu/signal.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index d5958278eba6d..91d4b6de58abe 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;
--
2.34.0.rc2.393.gf8c9666880-goog
next reply other threads:[~2021-11-26 13:36 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-26 12:47 Alexander Potapenko [this message]
2021-11-30 21:08 ` [PATCH] x86/fpu/signal: initialize sw_bytes in save_xstate_epilog() Dave Hansen
2021-11-30 21:38 ` Alexander Potapenko
2021-11-30 23:28 ` Marco Elver
2021-11-30 23:22 ` [tip: x86/urgent] x86/fpu/signal: Initialize " tip-bot2 for Marco Elver
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