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author | Peter Zijlstra <peterz@infradead.org> | 2019-07-08 15:55:30 -0500 |
---|---|---|
committer | Thomas Gleixner <tglx@linutronix.de> | 2019-07-09 22:39:15 +0200 |
commit | ecc606103837b98a2b665e8f14e533a6c72bbdc0 (patch) | |
tree | 13a82b9c7c38c22bc2a6fe14dba882076dc13134 /arch/x86/kernel | |
parent | 1cbec37b3f9cff074a67bef4fc34b30a09958a0a (diff) | |
download | linux-ecc606103837b98a2b665e8f14e533a6c72bbdc0.tar.bz2 |
x86/alternatives: Fix int3_emulate_call() selftest stack corruption
KASAN shows the following splat during boot:
BUG: KASAN: unknown-crash in unwind_next_frame+0x3f6/0x490
Read of size 8 at addr ffffffff84007db0 by task swapper/0
CPU: 0 PID: 0 Comm: swapper Tainted: G T 5.2.0-rc6-00013-g7457c0d #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
Call Trace:
dump_stack+0x19/0x1b
print_address_description+0x1b0/0x2b2
__kasan_report+0x10f/0x171
kasan_report+0x12/0x1c
__asan_load8+0x54/0x81
unwind_next_frame+0x3f6/0x490
unwind_next_frame+0x1b/0x23
arch_stack_walk+0x68/0xa5
stack_trace_save+0x7b/0xa0
save_trace+0x3c/0x93
mark_lock+0x1ef/0x9b1
lock_acquire+0x122/0x221
__mutex_lock+0xb6/0x731
mutex_lock_nested+0x16/0x18
_vm_unmap_aliases+0x141/0x183
vm_unmap_aliases+0x14/0x16
change_page_attr_set_clr+0x15e/0x2f2
set_memory_4k+0x2a/0x2c
check_bugs+0x11fd/0x1298
start_kernel+0x793/0x7eb
x86_64_start_reservations+0x55/0x76
x86_64_start_kernel+0x87/0xaa
secondary_startup_64+0xa4/0xb0
Memory state around the buggy address:
ffffffff84007c80: 00 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1
ffffffff84007d00: f1 00 00 00 00 00 00 00 00 00 f2 f2 f2 f3 f3 f3
>ffffffff84007d80: f3 79 be 52 49 79 be 00 00 00 00 00 00 00 00 f1
It turns out that int3_selftest() is corrupting the stack. The problem is
that the KASAN-ified version of int3_magic() is much less trivial than the
C code appears. It clobbers several unexpected registers. So when the
selftest's INT3 is converted to an emulated call to int3_magic(), the
registers are clobbered and Bad Things happen when the function returns.
Fix this by converting int3_magic() to the trivial ASM function it should
be, avoiding all calling convention issues. Also add ASM_CALL_CONSTRAINT to
the INT3 ASM, since it contains a 'CALL'.
[peterz: cribbed changelog from josh]
Fixes: 7457c0da024b ("x86/alternatives: Add int3_emulate_call() selftest")
Reported-by: kernel test robot <rong.a.chen@intel.com>
Debugged-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20190709125744.GB3402@hirez.programming.kicks-ass.net
Diffstat (limited to 'arch/x86/kernel')
-rw-r--r-- | arch/x86/kernel/alternative.c | 25 |
1 files changed, 20 insertions, 5 deletions
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index 99ef8b6f9a1a..ccd32013c47a 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -625,10 +625,23 @@ extern struct paravirt_patch_site __start_parainstructions[], * * See entry_{32,64}.S for more details. */ -static void __init int3_magic(unsigned int *ptr) -{ - *ptr = 1; -} + +/* + * We define the int3_magic() function in assembly to control the calling + * convention such that we can 'call' it from assembly. + */ + +extern void int3_magic(unsigned int *ptr); /* defined in asm */ + +asm ( +" .pushsection .init.text, \"ax\", @progbits\n" +" .type int3_magic, @function\n" +"int3_magic:\n" +" movl $1, (%" _ASM_ARG1 ")\n" +" ret\n" +" .size int3_magic, .-int3_magic\n" +" .popsection\n" +); extern __initdata unsigned long int3_selftest_ip; /* defined in asm below */ @@ -676,7 +689,9 @@ static void __init int3_selftest(void) "int3_selftest_ip:\n\t" __ASM_SEL(.long, .quad) " 1b\n\t" ".popsection\n\t" - : : __ASM_SEL_RAW(a, D) (&val) : "memory"); + : ASM_CALL_CONSTRAINT + : __ASM_SEL_RAW(a, D) (&val) + : "memory"); BUG_ON(val != 1); |