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x86/mm/mem_encrypt: Disable all instrumentation for early SME setup

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Enablement of AMD's Secure Memory Encryption feature is determined very
early after start_kernel() is entered. Part of this procedure involves
scanning the command line for the parameter 'mem_encrypt'.

To determine intended state, the function sme_enable() uses library
functions cmdline_find_option() and strncmp(). Their use occurs early
enough such that it cannot be assumed that any instrumentation subsystem
is initialized.

For example, making calls to a KASAN-instrumented function before KASAN
is set up will result in the use of uninitialized memory and a boot
failure.

When AMD's SME support is enabled, conditionally disable instrumentation
of these dependent functions in lib/string.c and arch/x86/lib/cmdline.c.

 [ bp: Get rid of intermediary nostackp var and cleanup whitespace. ]

Fixes: aca20d5462 ("x86/mm: Add support to make use of Secure Memory Encryption")
Reported-by: Li RongQing <[email protected]>
Signed-off-by: Gary R Hook <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Andy Shevchenko <[email protected]>
Cc: Boris Brezillon <[email protected]>
Cc: Coly Li <[email protected]>
Cc: "[email protected]" <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Kent Overstreet <[email protected]>
Cc: "[email protected]" <[email protected]>
Cc: Masahiro Yamada <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: "[email protected]" <[email protected]>
Cc: "[email protected]" <[email protected]>
Cc: Sebastian Andrzej Siewior <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: x86-ml <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
This commit is contained in:
Gary Hook 2019-04-29 22:22:58 +00:00 • committed by Borislav Petkov
commit b51ce3744f
2 changed files with 23 additions and 0 deletions
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11
lib/Makefile
View file

@ -17,6 +17,17 @@ KCOV_INSTRUMENT_list_debug.o := n
KCOV_INSTRUMENT_debugobjects.o := n
KCOV_INSTRUMENT_dynamic_debug.o := n
# Early boot use of cmdline, don't instrument it
ifdef CONFIG_AMD_MEM_ENCRYPT
KASAN_SANITIZE_string.o := n
ifdef CONFIG_FUNCTION_TRACER
CFLAGS_REMOVE_string.o = -pg
endif
CFLAGS_string.o := $(call cc-option, -fno-stack-protector)
endif
lib-y := ctype.o string.o vsprintf.o cmdline.o \
rbtree.o radix-tree.o timerqueue.o xarray.o \
idr.o int_sqrt.o extable.o \