From: Christoph Hellwig <hch@xxxxxx> commit 8d92db5c04d10381f4db70ed99b1b576f5db18a7 upstream. [Conflicts due to applying hunks only to the functions that were taken in 6ae08ae3dea2 upstream commit backport earlier] Instead of using the dangerous probe_kernel_read and strncpy_from_unsafe helpers, rework the compat probes to check if an address is a kernel or userspace one, and then use the low-level kernel or user probe helper shared by the proper kernel and user probe helpers. This slightly changes behavior as the compat probe on a user address doesn't check the lockdown flags, just as the pure user probes do. Signed-off-by: Christoph Hellwig <hch@xxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Alexei Starovoitov <ast@xxxxxxxxxx> Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxx> Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Link: http://lkml.kernel.org/r/20200521152301.2587579-14-hch@xxxxxx Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> --- kernel/trace/bpf_trace.c | 93 +++++++++++++++++++++++++++------------- 1 file changed, 64 insertions(+), 29 deletions(-) diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index d1fd13a47bdf..a46256f99229 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -139,65 +139,99 @@ static const struct bpf_func_proto bpf_override_return_proto = { #endif static __always_inline int -bpf_probe_read_kernel_common(void *dst, u32 size, const void *unsafe_ptr, - const bool compat) +bpf_probe_read_user_common(void *dst, u32 size, const void __user *unsafe_ptr) { - int ret = security_locked_down(LOCKDOWN_BPF_READ); + int ret; + ret = probe_user_read(dst, unsafe_ptr, size); if (unlikely(ret < 0)) - goto out; - ret = compat ? probe_kernel_read(dst, unsafe_ptr, size) : - probe_kernel_read_strict(dst, unsafe_ptr, size); - if (unlikely(ret < 0)) -out: memset(dst, 0, size); return ret; } -BPF_CALL_3(bpf_probe_read_compat, void *, dst, u32, size, - const void *, unsafe_ptr) +static __always_inline int +bpf_probe_read_user_str_common(void *dst, u32 size, + const void __user *unsafe_ptr) { - return bpf_probe_read_kernel_common(dst, size, unsafe_ptr, true); + int ret; + + ret = strncpy_from_user_nofault(dst, unsafe_ptr, size); + if (unlikely(ret < 0)) + memset(dst, 0, size); + return ret; } -static const struct bpf_func_proto bpf_probe_read_compat_proto = { - .func = bpf_probe_read_compat, - .gpl_only = true, - .ret_type = RET_INTEGER, - .arg1_type = ARG_PTR_TO_UNINIT_MEM, - .arg2_type = ARG_CONST_SIZE_OR_ZERO, - .arg3_type = ARG_ANYTHING, -}; +static __always_inline int +bpf_probe_read_kernel_common(void *dst, u32 size, const void *unsafe_ptr) +{ + int ret = security_locked_down(LOCKDOWN_BPF_READ); + + if (unlikely(ret < 0)) + goto fail; + ret = probe_kernel_read_strict(dst, unsafe_ptr, size); + if (unlikely(ret < 0)) + goto fail; + return ret; +fail: + memset(dst, 0, size); + return ret; +} static __always_inline int -bpf_probe_read_kernel_str_common(void *dst, u32 size, const void *unsafe_ptr, - const bool compat) +bpf_probe_read_kernel_str_common(void *dst, u32 size, const void *unsafe_ptr) { int ret = security_locked_down(LOCKDOWN_BPF_READ); if (unlikely(ret < 0)) - goto out; + goto fail; + /* - * The strncpy_from_unsafe_*() call will likely not fill the entire - * buffer, but that's okay in this circumstance as we're probing + * The strncpy_from_kernel_nofault() call will likely not fill the + * entire buffer, but that's okay in this circumstance as we're probing * arbitrary memory anyway similar to bpf_probe_read_*() and might * as well probe the stack. Thus, memory is explicitly cleared * only in error case, so that improper users ignoring return * code altogether don't copy garbage; otherwise length of string * is returned that can be used for bpf_perf_event_output() et al. */ - ret = compat ? strncpy_from_unsafe(dst, unsafe_ptr, size) : - strncpy_from_kernel_nofault(dst, unsafe_ptr, size); + ret = strncpy_from_kernel_nofault(dst, unsafe_ptr, size); if (unlikely(ret < 0)) -out: - memset(dst, 0, size); + goto fail; + + return 0; +fail: + memset(dst, 0, size); return ret; } +#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE +BPF_CALL_3(bpf_probe_read_compat, void *, dst, u32, size, + const void *, unsafe_ptr) +{ + if ((unsigned long)unsafe_ptr < TASK_SIZE) { + return bpf_probe_read_user_common(dst, size, + (__force void __user *)unsafe_ptr); + } + return bpf_probe_read_kernel_common(dst, size, unsafe_ptr); +} + +static const struct bpf_func_proto bpf_probe_read_compat_proto = { + .func = bpf_probe_read_compat, + .gpl_only = true, + .ret_type = RET_INTEGER, + .arg1_type = ARG_PTR_TO_UNINIT_MEM, + .arg2_type = ARG_CONST_SIZE_OR_ZERO, + .arg3_type = ARG_ANYTHING, +}; + BPF_CALL_3(bpf_probe_read_compat_str, void *, dst, u32, size, const void *, unsafe_ptr) { - return bpf_probe_read_kernel_str_common(dst, size, unsafe_ptr, true); + if ((unsigned long)unsafe_ptr < TASK_SIZE) { + return bpf_probe_read_user_str_common(dst, size, + (__force void __user *)unsafe_ptr); + } + return bpf_probe_read_kernel_str_common(dst, size, unsafe_ptr); } static const struct bpf_func_proto bpf_probe_read_compat_str_proto = { @@ -208,6 +242,7 @@ static const struct bpf_func_proto bpf_probe_read_compat_str_proto = { .arg2_type = ARG_CONST_SIZE_OR_ZERO, .arg3_type = ARG_ANYTHING, }; +#endif /* CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE */ BPF_CALL_3(bpf_probe_write_user, void __user *, unsafe_ptr, const void *, src, u32, size) -- 2.40.1
