[PATCH] powerpc/32s: Fix shift-out-of-bounds in KASAN init
Subsystems:
linux for powerpc (32-bit and 64-bit), the rest
STALE1737d
LANDED
Landed in mainline as af11dee4361b on 2021-11-30.
3 messages,
3 authors,
2021-12-07 · open the first message on its own page
================================================================================
UBSAN: shift-out-of-bounds in arch/powerpc/mm/kasan/book3s_32.c:22:23
shift exponent -1 is negative
CPU: 0 PID: 0 Comm: swapper Not tainted 5.15.5-gentoo-PowerMacG4 #9
Call Trace:
[c214be60] [c0ba0048] dump_stack_lvl+0x80/0xb0 (unreliable)
[c214be80] [c0b99288] ubsan_epilogue+0x10/0x5c
[c214be90] [c0b98fe0] __ubsan_handle_shift_out_of_bounds+0x94/0x138
[c214bf00] [c1c0f010] kasan_init_region+0xd8/0x26c
[c214bf30] [c1c0ed84] kasan_init+0xc0/0x198
[c214bf70] [c1c08024] setup_arch+0x18/0x54c
[c214bfc0] [c1c037f0] start_kernel+0x90/0x33c
[c214bff0] [00003610] 0x3610
================================================================================
This happens when the directly mapped memory is a power of 2.
Fix it by checking the shift and set the result to 0 when shift is -1
Reported-by: Erhard Furtner <redacted>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=215169
Fixes: 7974c4732642 ("powerpc/32s: Implement dedicated kasan_init_region()")
Signed-off-by: Christophe Leroy <redacted>
---
arch/powerpc/mm/kasan/book3s_32.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/mm/kasan/book3s_32.c b/arch/powerpc/mm/kasan/book3s_32.c
index 202bd260a009..35b287b0a8da 100644
--- a/arch/powerpc/mm/kasan/book3s_32.c
+++ b/arch/powerpc/mm/kasan/book3s_32.c
@@ -19,7 +19,8 @@ int __init kasan_init_region(void *start, size_t size)
block = memblock_alloc(k_size, k_size_base);
if (block && k_size_base >= SZ_128K && k_start == ALIGN(k_start, k_size_base)) {
- int k_size_more = 1 << (ffs(k_size - k_size_base) - 1);
+ int shift = ffs(k_size - k_size_base);
+ int k_size_more = shift ? 1 << (shift - 1) : 0;
setbat(-1, k_start, __pa(block), k_size_base, PAGE_KERNEL);
if (k_size_more >= SZ_128K)--
2.33.1
On Tue, 30 Nov 2021 09:42:37 +0100
Christophe Leroy [off-list ref] wrote:
quoted hunk
================================================================================
UBSAN: shift-out-of-bounds in arch/powerpc/mm/kasan/book3s_32.c:22:23
shift exponent -1 is negative
CPU: 0 PID: 0 Comm: swapper Not tainted 5.15.5-gentoo-PowerMacG4 #9
Call Trace:
[c214be60] [c0ba0048] dump_stack_lvl+0x80/0xb0 (unreliable)
[c214be80] [c0b99288] ubsan_epilogue+0x10/0x5c
[c214be90] [c0b98fe0] __ubsan_handle_shift_out_of_bounds+0x94/0x138
[c214bf00] [c1c0f010] kasan_init_region+0xd8/0x26c
[c214bf30] [c1c0ed84] kasan_init+0xc0/0x198
[c214bf70] [c1c08024] setup_arch+0x18/0x54c
[c214bfc0] [c1c037f0] start_kernel+0x90/0x33c
[c214bff0] [00003610] 0x3610
================================================================================
This happens when the directly mapped memory is a power of 2.
Fix it by checking the shift and set the result to 0 when shift is -1
Reported-by: Erhard Furtner <redacted>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=215169
Fixes: 7974c4732642 ("powerpc/32s: Implement dedicated kasan_init_region()")
Signed-off-by: Christophe Leroy <redacted>
---
arch/powerpc/mm/kasan/book3s_32.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/mm/kasan/book3s_32.c b/arch/powerpc/mm/kasan/book3s_32.c
index 202bd260a009..35b287b0a8da 100644
--- a/arch/powerpc/mm/kasan/book3s_32.c
+++ b/arch/powerpc/mm/kasan/book3s_32.c
@@ -19,7 +19,8 @@ int __init kasan_init_region(void *start, size_t size)
block = memblock_alloc(k_size, k_size_base);
if (block && k_size_base >= SZ_128K && k_start == ALIGN(k_start, k_size_base)) {
- int k_size_more = 1 << (ffs(k_size - k_size_base) - 1);
+ int shift = ffs(k_size - k_size_base);
+ int k_size_more = shift ? 1 << (shift - 1) : 0;
setbat(-1, k_start, __pa(block), k_size_base, PAGE_KERNEL);
if (k_size_more >= SZ_128K)--
2.33.1
Tested Christophes patch applied on 5.15.5 which works fine. Thanks!
I'll close the bugzilla report once it gets into stable.
Regards
Erhard
On Tue, 30 Nov 2021 09:42:37 +0100, Christophe Leroy wrote:
================================================================================
UBSAN: shift-out-of-bounds in arch/powerpc/mm/kasan/book3s_32.c:22:23
shift exponent -1 is negative
CPU: 0 PID: 0 Comm: swapper Not tainted 5.15.5-gentoo-PowerMacG4 #9
Call Trace:
[c214be60] [c0ba0048] dump_stack_lvl+0x80/0xb0 (unreliable)
[c214be80] [c0b99288] ubsan_epilogue+0x10/0x5c
[c214be90] [c0b98fe0] __ubsan_handle_shift_out_of_bounds+0x94/0x138
[c214bf00] [c1c0f010] kasan_init_region+0xd8/0x26c
[c214bf30] [c1c0ed84] kasan_init+0xc0/0x198
[c214bf70] [c1c08024] setup_arch+0x18/0x54c
[c214bfc0] [c1c037f0] start_kernel+0x90/0x33c
[c214bff0] [00003610] 0x3610
================================================================================
[...]
Applied to powerpc/next.
[1/1] powerpc/32s: Fix shift-out-of-bounds in KASAN init
https://git.kernel.org/powerpc/c/af11dee4361b3519981fa04d014873f9d9edd6ac
cheers