kernel/linux.git/arch/mips/net, branch v5.10.257

bpf, mips: Validate conditional branch offsets

2021-10-06T13:55:51+00:00

[ Upstream commit 37cb28ec7d3a36a5bace7063a3dba633ab110f8b ] The conditional branch instructions on MIPS use 18-bit signed offsets allowing for a branch range of 128 KBytes (backward and forward). However, this limit is not observed by the cBPF JIT compiler, and so the JIT compiler emits out-of-range branches when translating certain cBPF programs. A specific example of such a cBPF program is included in the "BPF_MAXINSNS: exec all MSH" test from lib/test_bpf.c that executes anomalous machine code containing incorrect branch offsets under JIT. Furthermore, this issue can be abused to craft undesirable machine code, where the control flow is hijacked to execute arbitrary Kernel code. The following steps can be used to reproduce the issue: # echo 1 > /proc/sys/net/core/bpf_jit_enable # modprobe test_bpf test_name="BPF_MAXINSNS: exec all MSH" This should produce multiple warnings from build_bimm() similar to: ------------[ cut here ]------------ WARNING: CPU: 0 PID: 209 at arch/mips/mm/uasm-mips.c:210 build_insn+0x558/0x590 Micro-assembler field overflow Modules linked in: test_bpf(+) CPU: 0 PID: 209 Comm: modprobe Not tainted 5.14.3 #1 Stack : 00000000 807bb824 82b33c9c 801843c0 00000000 00000004 00000000 63c9b5ee 82b33af4 80999898 80910000 80900000 82fd6030 00000001 82b33a98 82087180 00000000 00000000 80873b28 00000000 000000fc 82b3394c 00000000 2e34312e 6d6d6f43 809a180f 809a1836 6f6d203a 80900000 00000001 82b33bac 80900000 00027f80 00000000 00000000 807bb824 00000000 804ed790 001cc317 00000001 [...] Call Trace: [<80108f44>] show_stack+0x38/0x118 [<807a7aac>] dump_stack_lvl+0x5c/0x7c [<807a4b3c>] __warn+0xcc/0x140 [<807a4c3c>] warn_slowpath_fmt+0x8c/0xb8 [<8011e198>] build_insn+0x558/0x590 [<8011e358>] uasm_i_bne+0x20/0x2c [<80127b48>] build_body+0xa58/0x2a94 [<80129c98>] bpf_jit_compile+0x114/0x1e4 [<80613fc4>] bpf_prepare_filter+0x2ec/0x4e4 [<8061423c>] bpf_prog_create+0x80/0xc4 [] test_bpf_init+0x300/0xba8 [test_bpf] [<8010051c>] do_one_initcall+0x50/0x1d4 [<801c5e54>] do_init_module+0x60/0x220 [<801c8b20>] sys_finit_module+0xc4/0xfc [<801144d0>] syscall_common+0x34/0x58 [...] ---[ end trace a287d9742503c645 ]--- Then the anomalous machine code executes: => 0xc0a18000: addiu sp,sp,-16 0xc0a18004: sw s3,0(sp) 0xc0a18008: sw s4,4(sp) 0xc0a1800c: sw s5,8(sp) 0xc0a18010: sw ra,12(sp) 0xc0a18014: move s5,a0 0xc0a18018: move s4,zero 0xc0a1801c: move s3,zero # __BPF_STMT(BPF_LDX | BPF_B | BPF_MSH, 0) 0xc0a18020: lui t6,0x8012 0xc0a18024: ori t4,t6,0x9e14 0xc0a18028: li a1,0 0xc0a1802c: jalr t4 0xc0a18030: move a0,s5 0xc0a18034: bnez v0,0xc0a1ffb8 # incorrect branch offset 0xc0a18038: move v0,zero 0xc0a1803c: andi s4,s3,0xf 0xc0a18040: b 0xc0a18048 0xc0a18044: sll s4,s4,0x2 [...] # __BPF_STMT(BPF_LDX | BPF_B | BPF_MSH, 0) 0xc0a1ffa0: lui t6,0x8012 0xc0a1ffa4: ori t4,t6,0x9e14 0xc0a1ffa8: li a1,0 0xc0a1ffac: jalr t4 0xc0a1ffb0: move a0,s5 0xc0a1ffb4: bnez v0,0xc0a1ffb8 # incorrect branch offset 0xc0a1ffb8: move v0,zero 0xc0a1ffbc: andi s4,s3,0xf 0xc0a1ffc0: b 0xc0a1ffc8 0xc0a1ffc4: sll s4,s4,0x2 # __BPF_STMT(BPF_LDX | BPF_B | BPF_MSH, 0) 0xc0a1ffc8: lui t6,0x8012 0xc0a1ffcc: ori t4,t6,0x9e14 0xc0a1ffd0: li a1,0 0xc0a1ffd4: jalr t4 0xc0a1ffd8: move a0,s5 0xc0a1ffdc: bnez v0,0xc0a3ffb8 # correct branch offset 0xc0a1ffe0: move v0,zero 0xc0a1ffe4: andi s4,s3,0xf 0xc0a1ffe8: b 0xc0a1fff0 0xc0a1ffec: sll s4,s4,0x2 [...] # epilogue 0xc0a3ffb8: lw s3,0(sp) 0xc0a3ffbc: lw s4,4(sp) 0xc0a3ffc0: lw s5,8(sp) 0xc0a3ffc4: lw ra,12(sp) 0xc0a3ffc8: addiu sp,sp,16 0xc0a3ffcc: jr ra 0xc0a3ffd0: nop To mitigate this issue, we assert the branch ranges for each emit call that could generate an out-of-range branch. Fixes: 36366e367ee9 ("MIPS: BPF: Restore MIPS32 cBPF JIT") Fixes: c6610de353da ("MIPS: net: Add BPF JIT") Signed-off-by: Piotr Krysiuk Signed-off-by: Daniel Borkmann Tested-by: Johan Almbladh Acked-by: Johan Almbladh Cc: Paul Burton Cc: Thomas Bogendoerfer Link: https://lore.kernel.org/bpf/20210915160437.4080-1-piotras@gmail.com Signed-off-by: Sasha Levin

bpf: Introduce BPF nospec instruction for mitigating Spectre v4

2021-08-04T10:46:44+00:00

[ Upstream commit f5e81d1117501546b7be050c5fbafa6efd2c722c ] In case of JITs, each of the JIT backends compiles the BPF nospec instruction /either/ to a machine instruction which emits a speculation barrier /or/ to /no/ machine instruction in case the underlying architecture is not affected by Speculative Store Bypass or has different mitigations in place already. This covers both x86 and (implicitly) arm64: In case of x86, we use 'lfence' instruction for mitigation. In case of arm64, we rely on the firmware mitigation as controlled via the ssbd kernel parameter. Whenever the mitigation is enabled, it works for all of the kernel code with no need to provide any additional instructions here (hence only comment in arm64 JIT). Other archs can follow as needed. The BPF nospec instruction is specifically targeting Spectre v4 since i) we don't use a serialization barrier for the Spectre v1 case, and ii) mitigation instructions for v1 and v4 might be different on some archs. The BPF nospec is required for a future commit, where the BPF verifier does annotate intermediate BPF programs with speculation barriers. Co-developed-by: Piotr Krysiuk Co-developed-by: Benedict Schlueter Signed-off-by: Daniel Borkmann Signed-off-by: Piotr Krysiuk Signed-off-by: Benedict Schlueter Acked-by: Alexei Starovoitov Signed-off-by: Sasha Levin

MIPS: BPF: Use sizeof_field() instead of FIELD_SIZEOF()

2020-01-10T19:33:35+00:00

The FIELD_SIZEOF() macro was redundant, and is being removed from the kernel. Since commit c593642c8be0 ("treewide: Use sizeof_field() macro") this is one of the last users of the old macro, so replace it. Signed-off-by: Kees Cook Signed-off-by: Paul Burton Cc: linux-kernel@vger.kernel.org Cc: linux-mips@vger.kernel.org

MIPS: BPF: Restore MIPS32 cBPF JIT

2020-01-09T23:02:30+00:00

Commit 716850ab104d ("MIPS: eBPF: Initial eBPF support for MIPS32 architecture.") enabled our eBPF JIT for MIPS32 kernels, whereas it has previously only been availailable for MIPS64. It was my understanding at the time that the BPF test suite was passing & JITing a comparable number of tests to our cBPF JIT [1], but it turns out that was not the case. The eBPF JIT has a number of problems on MIPS32: - Most notably various code paths still result in emission of MIPS64 instructions which will cause reserved instruction exceptions & kernel panics when run on MIPS32 CPUs. - The eBPF JIT doesn't account for differences between the O32 ABI used by MIPS32 kernels versus the N64 ABI used by MIPS64 kernels. Notably arguments beyond the first 4 are passed on the stack in O32, and this is entirely unhandled when JITing a BPF_CALL instruction. Stack space must be reserved for arguments even if they all fit in registers, and the callee is free to assume that stack space has been reserved for its use - with the eBPF JIT this is not the case, so calling any function can result in clobbering values on the stack & unpredictable behaviour. Function arguments in eBPF are always 64-bit values which is also entirely unhandled - the JIT still uses a single (32-bit) register per argument. As a result all function arguments are always passed incorrectly when JITing a BPF_CALL instruction, leading to kernel crashes or strange behavior. - The JIT attempts to bail our on use of ALU64 instructions or 64-bit memory access instructions. The code doing this at the start of build_one_insn() incorrectly checks whether BPF_OP() equals BPF_DW, when it should really be checking BPF_SIZE() & only doing so when BPF_CLASS() is one of BPF_{LD,LDX,ST,STX}. This results in false positives that cause more bailouts than intended, and that in turns hides some of the problems described above. - The kernel's cBPF->eBPF translation makes heavy use of 64-bit eBPF instructions that the MIPS32 eBPF JIT bails out on, leading to most cBPF programs not being JITed at all. Until these problems are resolved, revert the removal of the cBPF JIT performed by commit 716850ab104d ("MIPS: eBPF: Initial eBPF support for MIPS32 architecture."). Together with commit f8fffebdea75 ("MIPS: BPF: Disable MIPS32 eBPF JIT") this restores MIPS32 BPF JIT behavior back to the same state it was prior to the introduction of the broken eBPF JIT support. [1] https://lore.kernel.org/linux-mips/MWHPR2201MB13583388481F01A422CE7D66D4410@MWHPR2201MB1358.namprd22.prod.outlook.com/ Signed-off-by: Paul Burton Fixes: 716850ab104d ("MIPS: eBPF: Initial eBPF support for MIPS32 architecture.") Cc: Daniel Borkmann Cc: Hassan Naveed Cc: Tony Ambardar Cc: bpf@vger.kernel.org Cc: netdev@vger.kernel.org Cc: linux-mips@vger.kernel.org Cc: linux-kernel@vger.kernel.org

Merge tag 'mips_fixes_5.5_1' of git://git.kernel.org/pub/scm/linux/kernel/git/mips/linux

2020-01-04T22:16:57+00:00

Pull MIPS fixes from Paul Burton: "A collection of MIPS fixes: - Fill the struct cacheinfo shared_cpu_map field with sensible values, notably avoiding issues with perf which was unhappy in the absence of these values. - A boot fix for Loongson 2E & 2F machines which was fallout from some refactoring performed this cycle. - A Kconfig dependency fix for the Loongson CPU HWMon driver. - A couple of VDSO fixes, ensuring gettimeofday() behaves appropriately for kernel configurations that don't include support for a clocksource the VDSO can use & fixing the calling convention for the n32 & n64 VDSOs which would previously clobber the $gp/$28 register. - A build fix for vmlinuz compressed images which were inappropriately building with -fsanitize-coverage despite not being part of the kernel proper, then failing to link due to the missing __sanitizer_cov_trace_pc() function. - A couple of eBPF JIT fixes, including disabling it for MIPS32 due to a large number of issues with the code generated there & reflecting ISA dependencies in Kconfig to enforce that systems which don't support the JIT must include the interpreter" * tag 'mips_fixes_5.5_1' of git://git.kernel.org/pub/scm/linux/kernel/git/mips/linux: MIPS: Avoid VDSO ABI breakage due to global register variable MIPS: BPF: eBPF JIT: check for MIPS ISA compliance in Kconfig MIPS: BPF: Disable MIPS32 eBPF JIT MIPS: Prevent link failure with kcov instrumentation MIPS: Kconfig: Use correct form for 'depends on' mips: Fix gettimeofday() in the vdso library MIPS: Fix boot on Fuloong2 systems mips: cacheinfo: report shared CPU map

MIPS: BPF: eBPF JIT: check for MIPS ISA compliance in Kconfig

2019-12-18T23:15:04+00:00

It is completely wrong to check for compile-time MIPS ISA revision in the body of bpf_int_jit_compile() as it may lead to get MIPS JIT fully omitted by the CC while the rest system will think that the JIT is actually present and works [1]. We can check if the selected CPU really supports MIPS eBPF JIT at configure time and avoid such situations when kernel can be built without both JIT and interpreter, but with CONFIG_BPF_SYSCALL=y. [1] https://lore.kernel.org/linux-mips/09d713a59665d745e21d021deeaebe0a@dlink.ru/ Fixes: 716850ab104d ("MIPS: eBPF: Initial eBPF support for MIPS32 architecture.") Cc: # v5.2+ Signed-off-by: Alexander Lobakin Signed-off-by: Paul Burton Cc: Ralf Baechle Cc: James Hogan Cc: Hassan Naveed Cc: Alexei Starovoitov Cc: Daniel Borkmann Cc: Martin KaFai Lau Cc: Song Liu Cc: Yonghong Song Cc: Andrii Nakryiko Cc: linux-mips@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: netdev@vger.kernel.org Cc: bpf@vger.kernel.org

bpf, mips: Limit to 33 tail calls

2019-12-11T12:57:22+00:00

All BPF JIT compilers except RISC-V's and MIPS' enforce a 33-tail calls limit at runtime. In addition, a test was recently added, in tailcalls2, to check this limit. This patch updates the tail call limit in MIPS' JIT compiler to allow 33 tail calls. Fixes: b6bd53f9c4e8 ("MIPS: Add missing file for eBPF JIT.") Reported-by: Mahshid Khezri Signed-off-by: Paul Chaignon Signed-off-by: Daniel Borkmann Acked-by: Martin KaFai Lau Link: https://lore.kernel.org/bpf/b8eb2caac1c25453c539248e56ca22f74b5316af.1575916815.git.paul.chaignon@gmail.com

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 441

2019-06-05T15:37:17+00:00

Based on 1 normalized pattern(s): this program is free software you can redistribute it and or modify it under the terms of the gnu general public license as published by the free software foundation version 2 of the license extracted by the scancode license scanner the SPDX license identifier GPL-2.0-only has been chosen to replace the boilerplate/reference in 315 file(s). Signed-off-by: Thomas Gleixner Reviewed-by: Allison Randal Reviewed-by: Armijn Hemel Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190531190115.503150771@linutronix.de Signed-off-by: Greg Kroah-Hartman

treewide: Add SPDX license identifier - Makefile/Kconfig

2019-05-21T08:50:46+00:00

Add SPDX license identifiers to all Make/Kconfig files which: - Have no license information of any form These files fall under the project license, GPL v2 only. The resulting SPDX license identifier is: GPL-2.0-only Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman

Merge tag 'mips_5.2' of git://git.kernel.org/pub/scm/linux/kernel/git/mips/linux

2019-05-08T23:41:47+00:00

Pull MIPS updates from Paul Burton: - A set of memblock initialization improvements thanks to Serge Semin, tidying up after our conversion from bootmem to memblock back in v4.20. - Our eBPF JIT the previously supported only MIPS64r2 through MIPS64r5 is improved to also support MIPS64r6. Support for MIPS32 systems is introduced, with the caveat that it only works for programs that don't use 64 bit registers or operations - those will bail out & need to be interpreted. - Improvements to the allocation & configuration of our exception vector that should fix issues seen on some platforms using recent versions of U-Boot. - Some minor improvements to code generated for jump labels, along with enabling them by default for generic kernels. * tag 'mips_5.2' of git://git.kernel.org/pub/scm/linux/kernel/git/mips/linux: (27 commits) mips: Manually call fdt_init_reserved_mem() method mips: Make sure dt memory regions are valid mips: Perform early low memory test mips: Dump memblock regions for debugging mips: Add reserve-nomap memory type support mips: Use memblock to reserve the __nosave memory range mips: Discard post-CMA-init foreach loop mips: Reserve memory for the kernel image resources MIPS: Remove duplicate EBase configuration MIPS: Sync icache for whole exception vector MIPS: Always allocate exception vector for MIPSr2+ MIPS: Use memblock_phys_alloc() for exception vector mips: Combine memblock init and memory reservation loops mips: Discard rudiments from bootmem_init mips: Make sure kernel .bss exists in boot mem pool mips: vdso: drop unnecessary cc-ldoption Revert "MIPS: ralink: fix cpu clock of mt7621 and add dt clk devices" MIPS: generic: Enable CONFIG_JUMP_LABEL MIPS: jump_label: Use compact branches for >= r6 MIPS: jump_label: Remove redundant nops ...