From: Christophe Leroy christophe.leroy@csgroup.eu
[ Upstream commit af11dee4361b3519981fa04d014873f9d9edd6ac ]
================================================================================ 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
Fixes: 7974c4732642 ("powerpc/32s: Implement dedicated kasan_init_region()") Reported-by: Erhard Furtner erhard_f@mailbox.org Signed-off-by: Christophe Leroy christophe.leroy@csgroup.eu Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://bugzilla.kernel.org/show_bug.cgi?id=215169 Link: https://lore.kernel.org/r/15cbc3439d4ad988b225e2119ec99502a5cc6ad3.163826174... Signed-off-by: Sasha Levin sashal@kernel.org --- 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 202bd260a0095..35b287b0a8da4 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)