linux-stable/lib/crypto
Jason A. Donenfeld d2a02e3c8b 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: 6048fdcc5f ("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>
2022-02-04 19:22:32 +01:00
..
aes.c crypto: aes - helper function to validate key length for AES algorithms 2019-08-09 15:11:43 +10:00
arc4.c
blake2s-generic.c lib/crypto: blake2s: include as built-in 2022-01-07 00:25:25 +01:00
blake2s-selftest.c lib/crypto: blake2s: move hmac construction into wireguard 2022-01-18 13:03:55 +01:00
blake2s.c lib/crypto: blake2s: avoid indirect calls to compression function for Clang CFI 2022-02-04 19:22:32 +01:00
chacha.c crypto: doc - fix kernel-doc notation in chacha.c and af_alg.c 2021-04-22 17:31:29 +10:00
chacha20poly1305-selftest.c crypto: arm64/chacha - correctly walk through blocks 2020-03-20 14:35:27 +11:00
chacha20poly1305.c crypto: lib - rename 'mod_init' & 'mod_exit' functions to be module-specific 2021-07-16 15:49:36 +08:00
curve25519-fiat32.c crypto: lib/curve25519 - work around Clang stack spilling issue 2019-11-17 09:02:43 +08:00
curve25519-generic.c crypto: curve25519 - Fix selftest build error 2020-01-16 15:18:13 +08:00
curve25519-hacl64.c crypto: curve25519 - generic C library implementations 2019-11-17 09:02:43 +08:00
curve25519-selftest.c crypto: lib/curve25519 - re-add selftests 2019-12-27 18:18:03 +08:00
curve25519.c crypto: lib - rename 'mod_init' & 'mod_exit' functions to be module-specific 2021-07-16 15:49:36 +08:00
des.c crypto: des - split off DES library from generic DES cipher driver 2019-08-22 14:57:33 +10:00
Kconfig lib/crypto: add prompts back to crypto libraries 2022-01-18 13:03:55 +01:00
libchacha.c crypto: chacha - move existing library code into lib/crypto 2019-11-17 09:02:39 +08:00
Makefile lib/crypto: blake2s: include as built-in 2022-01-07 00:25:25 +01:00
poly1305-donna32.c crypto: poly1305 - fix poly1305_core_setkey() declaration 2021-04-02 18:28:12 +11:00
poly1305-donna64.c crypto: poly1305 - fix poly1305_core_setkey() declaration 2021-04-02 18:28:12 +11:00
poly1305.c crypto: poly1305 - fix poly1305_core_setkey() declaration 2021-04-02 18:28:12 +11:00
sha256.c crypto: sha - split sha.h into sha1.h and sha2.h 2020-11-20 14:45:33 +11:00
sm4.c crypto: sm4 - Do not change section of ck and sbox 2021-09-17 11:05:10 +08:00