arm64/bpf: Remove 128MB limit for BPF JIT programs

commit b89ddf4cca43f1269093942cf5c4e457fd45c335 upstream.

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 <ard.biesheuvel@linaro.org>
Signed-off-by: Russell King <russell.king@oracle.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Alan Maguire <alan.maguire@oracle.com>
Link: https://lore.kernel.org/bpf/1636131046-5982-2-git-send-email-alan.maguire@oracle.com
Reviewed-by: Tom Saeger <tom.saeger@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/include/asm/extable.h b/arch/arm64/include/asm/extable.h
index b15eb4a3e6b20830e916720fb25503367f7818b9..840a35ed92ec8dd54a8d772420e936e54fd7098c 100644 (file)
--- 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 f1745a8434144a42c9d5a2a40253e27ca134e4b8..05886322c300c83876e2ec3fee00ffb0e6a2e33c 100644 (file)
--- 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   (_PAGE_END(VA_BITS_MIN))
-#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          (_PAGE_END(VA_BITS_MIN))
 #define MODULES_VSIZE          (SZ_128M)
 #define VMEMMAP_START          (-(UL(1) << (VA_BITS - VMEMMAP_SHIFT)))
 #define VMEMMAP_END            (VMEMMAP_START + VMEMMAP_SIZE)

diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index b03e383d944ab29ce925aeaaaa3b64c6a012e2b6..fe0cd0568813e91fceeeb1b82a1c28467be61ce9 100644 (file)
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -988,7 +988,7 @@ 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 aa0060178343a88a4d25f362ec8b0db2d2bda878..60a8b6a8a42b51614d578065ea1a0aca03604ae5 100644 (file)
--- 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));
-       if (!fixup)
-               return 0;
+       addr = instruction_pointer(regs);
 
-       if (in_bpf_jit(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;
+
        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 1c403536c9bb0390d5b762bc9ebcea6c7f0f5a97..9bc4066c5bf33a72401905790277fc5aa78900bc 100644 (file)
--- 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 803e7773fa869ab002c86cf8e9afbdfcf4119918..465c44d0c72fc1bba31ed3ac6f85decd3b357ca7 100644 (file)
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -1138,15 +1138,12 @@ 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)