Re: [BUG][PATCH] crypto: arm64: Avoid indirect branch to bti_c
From: Dave Martin <Dave.Martin@arm.com>
Date: 2020-10-06 10:43:21
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On Tue, Oct 06, 2020 at 11:25:11AM +0100, Catalin Marinas wrote:
On Tue, Oct 06, 2020 at 11:01:21AM +0100, Dave P Martin wrote:quoted
On Tue, Oct 06, 2020 at 09:27:48AM +0100, Will Deacon wrote:quoted
On Mon, Oct 05, 2020 at 10:48:54PM -0500, Jeremy Linton wrote:quoted
The AES code uses a 'br x7' as part of a function called by a macro. That branch needs a bti_j as a target. This results in a panic as seen below. Instead of trying to replace the branch target with a bti_jc, lets replace the indirect branch with a bl/ret, bl sequence that can target the existing bti_c. Bad mode in Synchronous Abort handler detected on CPU1, code 0x34000003 -- BTI CPU: 1 PID: 265 Comm: cryptomgr_test Not tainted 5.8.11-300.fc33.aarch64 #1 pstate: 20400c05 (nzCv daif +PAN -UAO BTYPE=j-) pc : aesbs_encrypt8+0x0/0x5f0 [aes_neon_bs] lr : aesbs_xts_encrypt+0x48/0xe0 [aes_neon_bs] sp : ffff80001052b730 aesbs_encrypt8+0x0/0x5f0 [aes_neon_bs] __xts_crypt+0xb0/0x2dc [aes_neon_bs] xts_encrypt+0x28/0x3c [aes_neon_bs] crypto_skcipher_encrypt+0x50/0x84 simd_skcipher_encrypt+0xc8/0xe0 crypto_skcipher_encrypt+0x50/0x84 test_skcipher_vec_cfg+0x224/0x5f0 test_skcipher+0xbc/0x120 alg_test_skcipher+0xa0/0x1b0 alg_test+0x3dc/0x47c cryptomgr_test+0x38/0x60 Fixes: commit 0e89640b640d ("crypto: arm64 - Use modern annotations for assembly functions")nit: the "commit" string shouldn't be here, and I think the linux-next scripts will yell at us if we don't remove it.quoted
Signed-off-by: Jeremy Linton <redacted> --- arch/arm64/crypto/aes-neonbs-core.S | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)diff --git a/arch/arm64/crypto/aes-neonbs-core.S b/arch/arm64/crypto/aes-neonbs-core.S index b357164379f6..32f53ebe5e2c 100644 --- a/arch/arm64/crypto/aes-neonbs-core.S +++ b/arch/arm64/crypto/aes-neonbs-core.S@@ -788,7 +788,7 @@ SYM_FUNC_START_LOCAL(__xts_crypt8) 0: mov bskey, x21 mov rounds, x22 - br x7 + retDang, replied on an old version.Which I ignored (by default, when the kbuild test robot complains ;)).quoted
Since this is logically a tail call, could we simply be using br x16 or br x17 for this? The architecture makes special provision for that so that the compiler can generate tail-calls.So a "br x16" is compatible with a bti_c landing pad. I think it makes more sense to keep it as a tail call.
Just to be clear, I'm happy either way, but I thought it would make sense to point this out. Normally, "bti j" would be used just for weird stuff like jump tables, but .S files all count as "weird stuff" to some extent -- so there are no hard and fast rules. Cheers ---Dave _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel