On Mon, 2018-10-01 at 06:21:51 UTC, Daniel Axtens wrote: > When enumerating page size definitions to check hardware support, > we construct a constant which is (1U << (def->shift - 10)). > > However, the array of page size definitions is only initalised for > various MMU_PAGE_* constants, so it contains a number of 0-initialised > elements with def->shift == 0. This means we end up shifting by a > very large number, which gives the following UBSan splat: > > ================================================================================ > UBSAN: Undefined behaviour in > /home/dja/dev/linux/linux/arch/powerpc/mm/tlb_nohash.c:506:21 > shift exponent 4294967286 is too large for 32-bit type 'unsigned int' > CPU: 0 PID: 0 Comm: swapper Not tainted 4.19.0-rc3-00045-ga604f927b012-dirty > #6 > Call Trace: > [c00000000101bc20] [c000000000a13d54] .dump_stack+0xa8/0xec (unreliable) > [c00000000101bcb0] [c0000000004f20a8] .ubsan_epilogue+0x18/0x64 > [c00000000101bd30] [c0000000004f2b10] > .__ubsan_handle_shift_out_of_bounds+0x110/0x1a4 > [c00000000101be20] [c000000000d21760] .early_init_mmu+0x1b4/0x5a0 > [c00000000101bf10] [c000000000d1ba28] .early_setup+0x100/0x130 > [c00000000101bf90] [c000000000000528] start_here_multiplatform+0x68/0x80 > ================================================================================ > > Fix this by first checking if the element exists (shift != 0) before > constructing the constant. > > Signed-off-by: Daniel Axtens <d...@axtens.net>
Applied to powerpc next, thanks. https://git.kernel.org/powerpc/c/f5e284803a7206d43e26f9ffcae5de cheers
