From: Borislav Petkov <[email protected]>
Commit
24c2503255d3 ("x86/microcode: Do not access the initrd after it has been
freed")
fixed attempts to access initrd from the microcode loader after it has
been freed. However, a similar KASAN warning was reported (stack trace
edited):
smpboot: Booting Node 0 Processor 1 APIC 0x11
==================================================================
BUG: KASAN: use-after-free in find_cpio_data+0x9b5/0xa50
Read of size 1 at addr ffff880035ffd000 by task swapper/1/0
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.14.8-slack #7
Hardware name: System manufacturer System Product Name/A88X-PLUS, BIOS 3003
03/10/2016
Call Trace:
dump_stack
print_address_description
kasan_report
? find_cpio_data
__asan_report_load1_noabort
find_cpio_data
find_microcode_in_initrd
__load_ucode_amd
load_ucode_amd_ap
load_ucode_ap
After some investigation, it turned out that a merge was done using the
wrong side to resolve, leading to picking up the previous state, before
the 24c2503255d3 fix. Therefore the Fixes tag below contains a merge
commit.
Revert the mismerge by catching the save_microcode_in_initrd_amd()
retval and thus letting the function exit with the last return statement
so that initrd_gone can be set to true.
Reported-by: <[email protected]>
Cc: <[email protected]> # 4.11
Fixes: f26483eaedec ("Merge branch 'x86/urgent' into x86/microcode, to resolve
conflicts")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=198295
Signed-off-by: Borislav Petkov <[email protected]>
---
arch/x86/kernel/cpu/microcode/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kernel/cpu/microcode/core.c
b/arch/x86/kernel/cpu/microcode/core.c
index c4fa4a85d4cb..e4fc595cd6ea 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -239,7 +239,7 @@ static int __init save_microcode_in_initrd(void)
break;
case X86_VENDOR_AMD:
if (c->x86 >= 0x10)
- return save_microcode_in_initrd_amd(cpuid_eax(1));
+ ret = save_microcode_in_initrd_amd(cpuid_eax(1));
break;
default:
break;
--
2.13.0
