On Fri, Jan 21, 2022 at 11:17 AM Jason A. Donenfeld <Jason@xxxxxxxxx> wrote: > > blake2s_compress_generic is weakly aliased to blake2s_generic. The > current harness for function selection uses a function pointer, which is > ordinarily inlined and resolved at compile time. But when Clang's CFI is > enabled, CFI still triggers when making an indirect call via a weak > symbol. This seems like a bug in Clang's CFI, as though it's bucketing > weak symbols and strong symbols differently. It also only seems to > trigger when "full LTO" mode is used, rather than "thin LTO". > > [ 0.000000][ T0] Kernel panic - not syncing: CFI failure (target: blake2s_compress_generic+0x0/0x1444) > [ 0.000000][ T0] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.16.0-mainline-06981-g076c855b846e #1 > [ 0.000000][ T0] Hardware name: MT6873 (DT) > [ 0.000000][ T0] Call trace: > [ 0.000000][ T0] dump_backtrace+0xfc/0x1dc > [ 0.000000][ T0] dump_stack_lvl+0xa8/0x11c > [ 0.000000][ T0] panic+0x194/0x464 > [ 0.000000][ T0] __cfi_check_fail+0x54/0x58 > [ 0.000000][ T0] __cfi_slowpath_diag+0x354/0x4b0 > [ 0.000000][ T0] blake2s_update+0x14c/0x178 > [ 0.000000][ T0] _extract_entropy+0xf4/0x29c > [ 0.000000][ T0] crng_initialize_primary+0x24/0x94 > [ 0.000000][ T0] rand_initialize+0x2c/0x6c > [ 0.000000][ T0] start_kernel+0x2f8/0x65c > [ 0.000000][ T0] __primary_switched+0xc4/0x7be4 > [ 0.000000][ T0] Rebooting in 5 seconds.. YongQin also reported hitting this issue(also, only in the LTO=full case) on the db845c dev board. Sami pointed me to this patch and I just wanted to confirm it gets things booting again. Reported-by: YongQin Liu <yongqin.liu@xxxxxxxxxx> Tested-by: John Stultz <john.stultz@xxxxxxxxxx> Thanks so much for the quick analysis and fix! -john
