Messages in this thread | | | Date | Tue, 30 Nov 2021 14:45:41 +0100 | From | "Erhard F." <> | Subject | Re: [PATCH] powerpc/32s: Fix shift-out-of-bounds in KASAN init |
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On Tue, 30 Nov 2021 09:42:37 +0100 Christophe Leroy <christophe.leroy@csgroup.eu> 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 > ================================================================================ > > 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 <erhard_f@mailbox.org> > Link: https://bugzilla.kernel.org/show_bug.cgi?id=215169 > Fixes: 7974c4732642 ("powerpc/32s: Implement dedicated kasan_init_region()") > Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> > --- > 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
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