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author | Jason A. Donenfeld <Jason@zx2c4.com> | 2022-01-19 14:35:06 +0100 |
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committer | Jason A. Donenfeld <Jason@zx2c4.com> | 2022-02-04 19:22:32 +0100 |
commit | 7fdf5a84d5c550ebc16253f6623283e27d7e54ae (patch) | |
tree | 36f1e901cd0e7e3b299d9e9c1051fa193e8d85aa /crypto/wp512.c | |
parent | 46d5407e0ad4bd4a8e3fdcec98127a99bef6e212 (diff) | |
download | linux-crypto-7fdf5a84d5c550ebc16253f6623283e27d7e54ae.tar.gz linux-crypto-7fdf5a84d5c550ebc16253f6623283e27d7e54ae.zip |
lib/crypto: blake2s: avoid indirect calls to compression function for Clang CFI
blake2s_compress_generic is weakly aliased by blake2s_compress. 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..
Nonetheless, the function pointer method isn't so terrific anyway, so
this patch replaces it with a simple boolean, which also gets inlined
away. This successfully works around the Clang bug.
In general, I'm not too keen on all of the indirection involved here; it
clearly does more harm than good. Hopefully the whole thing can get
cleaned up down the road when lib/crypto is overhauled more
comprehensively. But for now, we go with a simple bandaid.
Fixes: 21e8583d107d ("lib/crypto: blake2s: include as built-in")
Link: https://github.com/ClangBuiltLinux/linux/issues/1567
Reported-by: Miles Chen <miles.chen@mediatek.com>
Tested-by: Miles Chen <miles.chen@mediatek.com>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: John Stultz <john.stultz@linaro.org>
Acked-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Diffstat (limited to 'crypto/wp512.c')
0 files changed, 0 insertions, 0 deletions