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ANDROID: arm64: bpf: implement arch_bpf_jit_check_func

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Implement arch_bpf_jit_check_func to check that pointers to jited BPF
functions are correctly aligned and point to the BPF JIT region. This
narrows down the attack surface on the stored pointer.

Bug: 140377409
Change-Id: I10c448eda6a8b0bf4c16ee591fc65974696216b9
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
(cherry picked from commit c10baf7606)
This commit is contained in:
Sami Tolvanen 2019-09-04 14:56:40 -07:00 committed by Maciej Żenczykowski
parent 89aed473c5
commit cfd89c3d47
1 changed files with 22 additions and 0 deletions
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22
arch/arm64/net/bpf_jit_comp.c
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@ -949,3 +949,25 @@ out:
tmp : orig_prog);
return prog;
}
#ifdef CONFIG_CFI_CLANG
bool arch_bpf_jit_check_func(const struct bpf_prog *prog)
{
const uintptr_t func = (const uintptr_t)prog->bpf_func;
/*
* bpf_func must be correctly aligned and within the correct region.
* module_alloc places JIT code in the module region, unless
* ARM64_MODULE_PLTS is enabled, in which case we might end up using
* the vmalloc region too.
*/
if (unlikely(!IS_ALIGNED(func, sizeof(u32))))
return false;
if (IS_ENABLED(CONFIG_ARM64_MODULE_PLTS) &&
is_vmalloc_addr(prog->bpf_func))
return true;
return (func >= MODULES_VADDR && func < MODULES_END);
}
#endif