From 75d066563906b46e5960369be698032df1dea03a Mon Sep 17 00:00:00 2001 From: Russell King Date: Fri, 5 Nov 2021 16:50:45 +0000 Subject: [PATCH] BACKPORT: arm64/bpf: Remove 128MB limit for BPF JIT programs (Backport: resolve conflicts due to missing f4693c2716b35 and also drop in_bpf_jit from fixup_exception the same way 5.15 backport 9c82ce593626 does it.) Commit 91fc957c9b1d ("arm64/bpf: don't allocate BPF JIT programs in module memory") restricts BPF JIT program allocation to a 128MB region to ensure BPF programs are still in branching range of each other. However this restriction should not apply to the aarch64 JIT, since BPF_JMP | BPF_CALL are implemented as a 64-bit move into a register and then a BLR instruction - which has the effect of being able to call anything without proximity limitation. The practical reason to relax this restriction on JIT memory is that 128MB of JIT memory can be quickly exhausted, especially where PAGE_SIZE is 64KB - one page is needed per program. In cases where seccomp filters are applied to multiple VMs on VM launch - such filters are classic BPF but converted to BPF - this can severely limit the number of VMs that can be launched. In a world where we support BPF JIT always on, turning off the JIT isn't always an option either. Fixes: 91fc957c9b1d ("arm64/bpf: don't allocate BPF JIT programs in module memory") Suggested-by: Ard Biesheuvel Signed-off-by: Russell King Signed-off-by: Daniel Borkmann Tested-by: Alan Maguire Link: https://lore.kernel.org/bpf/1636131046-5982-2-git-send-email-alan.maguire@oracle.com (cherry picked from commit b89ddf4cca43f1269093942cf5c4e457fd45c335) Bug: 252919296 Change-Id: Iec7d0b2bba001df94c2e21fcd5883ff002111cd5 Signed-off-by: Andrey Konovalov --- arch/arm64/include/asm/extable.h | 9 --------- arch/arm64/include/asm/memory.h | 5 +---- arch/arm64/kernel/traps.c | 2 +- arch/arm64/mm/extable.c | 13 +++++++++---- arch/arm64/mm/ptdump.c | 2 -- arch/arm64/net/bpf_jit_comp.c | 7 ++----- 6 files changed, 13 insertions(+), 25 deletions(-) diff --git a/arch/arm64/include/asm/extable.h b/arch/arm64/include/asm/extable.h index b15eb4a3e6b2..840a35ed92ec 100644 --- a/arch/arm64/include/asm/extable.h +++ b/arch/arm64/include/asm/extable.h @@ -22,15 +22,6 @@ struct exception_table_entry #define ARCH_HAS_RELATIVE_EXTABLE -static inline bool in_bpf_jit(struct pt_regs *regs) -{ - if (!IS_ENABLED(CONFIG_BPF_JIT)) - return false; - - return regs->pc >= BPF_JIT_REGION_START && - regs->pc < BPF_JIT_REGION_END; -} - #ifdef CONFIG_BPF_JIT int arm64_bpf_fixup_exception(const struct exception_table_entry *ex, struct pt_regs *regs); diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h index b864fdb79df0..a1f0e752d1cd 100644 --- a/arch/arm64/include/asm/memory.h +++ b/arch/arm64/include/asm/memory.h @@ -44,11 +44,8 @@ #define _PAGE_OFFSET(va) (-(UL(1) << (va))) #define PAGE_OFFSET (_PAGE_OFFSET(VA_BITS)) #define KIMAGE_VADDR (MODULES_END) -#define BPF_JIT_REGION_START (KASAN_SHADOW_END) -#define BPF_JIT_REGION_SIZE (SZ_128M) -#define BPF_JIT_REGION_END (BPF_JIT_REGION_START + BPF_JIT_REGION_SIZE) #define MODULES_END (MODULES_VADDR + MODULES_VSIZE) -#define MODULES_VADDR (BPF_JIT_REGION_END) +#define MODULES_VADDR (KASAN_SHADOW_END) #define MODULES_VSIZE (SZ_128M) #define VMEMMAP_START (-VMEMMAP_SIZE - SZ_2M) #define VMEMMAP_END (VMEMMAP_START + VMEMMAP_SIZE) diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index acc7e7647cbb..a6ba4362e36d 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -931,7 +931,7 @@ static struct break_hook bug_break_hook = { static int reserved_fault_handler(struct pt_regs *regs, unsigned int esr) { pr_err("%s generated an invalid instruction at %pS!\n", - in_bpf_jit(regs) ? "BPF JIT" : "Kernel text patching", + "Kernel text patching", (void *)instruction_pointer(regs)); /* We cannot handle this */ diff --git a/arch/arm64/mm/extable.c b/arch/arm64/mm/extable.c index aa0060178343..60a8b6a8a42b 100644 --- a/arch/arm64/mm/extable.c +++ b/arch/arm64/mm/extable.c @@ -9,14 +9,19 @@ int fixup_exception(struct pt_regs *regs) { const struct exception_table_entry *fixup; + unsigned long addr; - fixup = search_exception_tables(instruction_pointer(regs)); + addr = instruction_pointer(regs); + + /* Search the BPF tables first, these are formatted differently */ + fixup = search_bpf_extables(addr); + if (fixup) + return arm64_bpf_fixup_exception(fixup, regs); + + fixup = search_exception_tables(addr); if (!fixup) return 0; - if (in_bpf_jit(regs)) - return arm64_bpf_fixup_exception(fixup, regs); - regs->pc = (unsigned long)&fixup->fixup + fixup->fixup; return 1; } diff --git a/arch/arm64/mm/ptdump.c b/arch/arm64/mm/ptdump.c index 04137a8f3d2d..bf8ddeac5d8f 100644 --- a/arch/arm64/mm/ptdump.c +++ b/arch/arm64/mm/ptdump.c @@ -41,8 +41,6 @@ static struct addr_marker address_markers[] = { { 0 /* KASAN_SHADOW_START */, "Kasan shadow start" }, { KASAN_SHADOW_END, "Kasan shadow end" }, #endif - { BPF_JIT_REGION_START, "BPF start" }, - { BPF_JIT_REGION_END, "BPF end" }, { MODULES_VADDR, "Modules start" }, { MODULES_END, "Modules end" }, { VMALLOC_START, "vmalloc() area" }, diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index 9097e90d07e2..86a252da69ab 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -1148,15 +1148,12 @@ out: u64 bpf_jit_alloc_exec_limit(void) { - return BPF_JIT_REGION_SIZE; + return VMALLOC_END - VMALLOC_START; } void *bpf_jit_alloc_exec(unsigned long size) { - return __vmalloc_node_range(size, PAGE_SIZE, BPF_JIT_REGION_START, - BPF_JIT_REGION_END, GFP_KERNEL, - PAGE_KERNEL, 0, NUMA_NO_NODE, - __builtin_return_address(0)); + return vmalloc(size); } void bpf_jit_free_exec(void *addr)