This Linux kernel change "crypto: sha512/arm – fix crash bug in Thumb2 build" is included in the Linux 5.0 release. This change is authored by Ard Biesheuvel <ard.biesheuvel [at] linaro.org> on Sat Feb 16 14:51:26 2019 +0100. The commit for this change in Linux stable tree is c643165 (patch).
crypto: sha512/arm - fix crash bug in Thumb2 build The SHA512 code we adopted from the OpenSSL project uses a rather peculiar way to take the address of the round constant table: it takes the address of the sha256_block_data_order() routine, and substracts a constant known quantity to arrive at the base of the table, which is emitted by the same assembler code right before the routine's entry point. However, recent versions of binutils have helpfully changed the behavior of references emitted via an ADR instruction when running in Thumb2 mode: it now takes the Thumb execution mode bit into account, which is bit 0 af the address. This means the produced table address also has bit 0 set, and so we end up with an address value pointing 1 byte past the start of the table, which results in crashes such as Unable to handle kernel paging request at virtual address bf825000 pgd = 42f44b11 [bf825000] *pgd=80000040206003, *pmd=5f1bd003, *pte=00000000 Internal error: Oops: 207 [#1] PREEMPT SMP THUMB2 Modules linked in: sha256_arm(+) sha1_arm_ce sha1_arm ... CPU: 7 PID: 396 Comm: cryptomgr_test Not tainted 5.0.0-rc6+ #144 Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015 PC is at sha256_block_data_order+0xaaa/0xb30 [sha256_arm] LR is at __this_module+0x17fd/0xffffe800 [sha256_arm] pc : [<bf820bca>] lr : [<bf824ffd>] psr: 800b0033 sp : ebc8bbe8 ip : faaabe1c fp : 2fdd3433 r10: 4c5f1692 r9 : e43037df r8 : b04b0a5a r7 : c369d722 r6 : 39c3693e r5 : 7a013189 r4 : 1580d26b r3 : 8762a9b0 r2 : eea9c2cd r1 : 3e9ab536 r0 : 1dea4ae7 Flags: Nzcv IRQs on FIQs on Mode SVC_32 ISA Thumb Segment user Control: 70c5383d Table: 6b8467c0 DAC: dbadc0de Process cryptomgr_test (pid: 396, stack limit = 0x69e1fe23) Stack: (0xebc8bbe8 to 0xebc8c000) ... unwind: Unknown symbol address bf820bca unwind: Index not found bf820bca Code: 441a ea80 40f9 440a (f85e) 3b04 ---[ end trace e560cce92700ef8a ]--- Given that this affects older kernels as well, in case they are built with a recent toolchain, apply a minimal backportable fix, which is to emit another non-code label at the start of the routine, and reference that instead. (This is similar to the current upstream state of this file in OpenSSL) Signed-off-by: Ard Biesheuvel <[email protected]> Signed-off-by: Herbert Xu <[email protected]>
There are 6 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.
arch/arm/crypto/sha512-armv4.pl | 3 ++- arch/arm/crypto/sha512-core.S_shipped | 3 ++- 2 files changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/arm/crypto/sha512-armv4.pl b/arch/arm/crypto/sha512-armv4.pl index fb5d150..788c17b 100644 --- a/arch/arm/crypto/sha512-armv4.pl +++ b/arch/arm/crypto/sha512-armv4.pl @@ -274,10 +274,11 @@ WORD64(0x5fcb6fab,0x3ad6faec, 0x6c44198c,0x4a475817) .global sha512_block_data_order .type sha512_block_data_order,%function sha512_block_data_order: +.Lsha512_block_data_order: #if __ARM_ARCH__<7 sub r3,pc,#8 @ sha512_block_data_order #else - adr r3,sha512_block_data_order + adr r3,.Lsha512_block_data_order #endif #if __ARM_MAX_ARCH__>=7 && !defined(__KERNEL__) ldr r12,.LOPENSSL_armcap diff --git a/arch/arm/crypto/sha512-core.S_shipped b/arch/arm/crypto/sha512-core.S_shipped index b1c334a..710ea30 100644 --- a/arch/arm/crypto/sha512-core.S_shipped +++ b/arch/arm/crypto/sha512-core.S_shipped @@ -141,10 +141,11 @@ WORD64(0x5fcb6fab,0x3ad6faec, 0x6c44198c,0x4a475817) .global sha512_block_data_order .type sha512_block_data_order,%function sha512_block_data_order: +.Lsha512_block_data_order: #if __ARM_ARCH__<7 sub r3,pc,#8 @ sha512_block_data_order #else - adr r3,sha512_block_data_order + adr r3,.Lsha512_block_data_order #endif #if __ARM_MAX_ARCH__>=7 && !defined(__KERNEL__) ldr r12,.LOPENSSL_armcap