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bh=wU2N1BOhyNmMdvHXU/2VocFu1lHdohwPll/T20B+ryE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=bvAxYlu5Q0RwXXod4VhvsywM0NXgCR44VayRB0M1gpt3A6LERtbk3mFI5hhO3w5PU flixUhFphzdspyyEVMn0I6QHJ696bgaToVc3xyjcC4kmOK9yvhx3PqOBOWA2D2aFkF 8ytcYLfMLqqvfYUe4OuFiCPd4TynSPkMxnhswgkE7/niNtDl6mjYCUg7Tp5pLMp9wx UR9zQpkB09m2STIPWImCiraooij2D52CkbHBJKcF5Wq/XBD+Bzjk1kgP+fFDtHXApH 7dD5myzKXsO7i9upbNvWN9nIuc1lzWAAriVD10AT8/69YaNunqgauei0EcVnj1MFuc sfIWwB+xT/mNQ== From: Jiri Olsa To: stable@vger.kernel.org Cc: Andrii Nakryiko , linux-mm@kvack.org, bpf@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, Masami Hiramatsu , Tsahee Zidenberg , Andrii Nakryiko , Christoph Hellwig , Daniel Borkmann , Thomas Gleixner , =?UTF-8?q?Mah=C3=A9=20Tardy?= , linux-arm-kernel@lists.infradead.org Subject: [RFC PATCH stable 5.4 2/8] bpf: Add probe_read_{user, kernel} and probe_read_{user, kernel}_str helpers Date: Mon, 22 May 2023 22:33:46 +0200 Message-Id: <20230522203352.738576-3-jolsa@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20230522203352.738576-1-jolsa@kernel.org> References: <20230522203352.738576-1-jolsa@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 574122000C X-Rspam-User: X-Stat-Signature: j3tz9d7xz75tu1jmgts4p4xyhr57iw4j X-Rspamd-Server: rspam01 X-HE-Tag: 1684787671-181363 X-HE-Meta: U2FsdGVkX1/wPbR4vMkX/P0SCZISHlJAOWgHfQdHEYuOv+qH6WY9RbiED9VrWq5ROoMZ07vG9vXKeSuviOfcVZnfM0Udwtnp8/hH3B2NL8ia5fu9XJ5F38cr38OuGdW7dX+8IWXAsxC8+oMwdNSfBnO23FozuqqUaBm0e3Pb2koXL2acgEzgaYbvuWk3e+u0U3ViFD8tCrEJzDMNsfALTj6u6EgcwSHnOv1Lv7rUVewSyFZgrfnLuLUnaXfq5nA8ATff24d3FlpH5DwGcArAd05SXHC+fLiDQLg8ze0R3YolIRUBIPrIAzSa/yQAlZtUmPvBlHIlru9Oa84c+u38EvunZEClk644O5T0cjDZk0JvCwMUTo3jD/V7b8IK/T3OAq2lB4YwjRpcE3CFiXzUjI+7uDw+3YZa2KUGH6iSqvfakAZn/bAS02a21zMHPhdTemN+i7Duy7I3r198YVrRQIw3hCMTMFlHL7shytiCUt2Ns739IeHS1JMnMtH+n9uk/MKTdOnPsV2nIvL9F+5Q97U+r4QaFYQfH/ITK0Rn4X+Lmtu+Ezr+SnQ8Ec20c1vissbH03GTmVoS8o9g1bZn2jTDRqrQG2qpPzlcYTG31z6FRtYF2cMpGDzXmY5VHWVWd33wObMoqZKPW97pIBxD+Iw1l0rSjtFwXwdvR84ZCf66yZz35OLGXrXAxVjL9Xdu7gIi12e/lH/DfJ9wHRtX0wWUtxCnDUNxQIHgNw3CYwRPxyqoGnrt9TO9YVu6lG7nHfcjpOziR0wK+VOI/XGa0uoP/2GsYkfX9PjTVCQD1aWNvJGwASwYtC+rsKqRlTpYaUnuKKj2VWkVqduQZTAuTIqL05ULqgI6MGEtimmVlQFki4FvYKSBvAqVDlUWsRRpbiSrRjSmqYHCSN7Tb0+/lXYUWZ8Z/SGH/2N24kTTIUa3yKRbh1ssfPn5OFmRc/tzuXGI5E61VRqJPJUwS+L XOuytoYM 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Daniel Borkmann commit 6ae08ae3dea2cfa03dd3665a3c8475c2d429ef47 upstream. [Taking only hunks that are related to probe_read and probe_read_str helpers, which we want to fix. Taking this patch/hunks as a base for following changes and ommiting the new helpers and uapi changes.] The current bpf_probe_read() and bpf_probe_read_str() helpers are broken in that they assume they can be used for probing memory access for kernel space addresses /as well as/ user space addresses. However, plain use of probe_kernel_read() for both cases will attempt to always access kernel space address space given access is performed under KERNEL_DS and some archs in-fact have overlapping address spaces where a kernel pointer and user pointer would have the /same/ address value and therefore accessing application memory via bpf_probe_read{,_str}() would read garbage values. Lets fix BPF side by making use of recently added 3d7081822f7f ("uaccess: Add non-pagefault user-space read functions"). Unfortunately, the only way to fix this status quo is to add dedicated bpf_probe_read_{user,kernel}() and bpf_probe_read_{user,kernel}_str() helpers. The bpf_probe_read{,_str}() helpers are kept as-is to retain their current behavior. The two *_user() variants attempt the access always under USER_DS set, the two *_kernel() variants will -EFAULT when accessing user memory if the underlying architecture has non-overlapping address ranges, also avoiding throwing the kernel warning via 00c42373d397 ("x86-64: add warning for non-canonical user access address dereferences"). Fixes: a5e8c07059d0 ("bpf: add bpf_probe_read_str helper") Fixes: 2541517c32be ("tracing, perf: Implement BPF programs attached to kprobes") Signed-off-by: Daniel Borkmann Signed-off-by: Alexei Starovoitov Acked-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/796ee46e948bc808d54891a1108435f8652c6ca4.1572649915.git.daniel@iogearbox.net --- kernel/trace/bpf_trace.c | 103 ++++++++++++++++++++++----------------- 1 file changed, 57 insertions(+), 46 deletions(-) diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 1e1345cd21b4..9ac27d48cc8e 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -138,24 +138,70 @@ static const struct bpf_func_proto bpf_override_return_proto = { }; #endif -BPF_CALL_3(bpf_probe_read, void *, dst, u32, size, const void *, unsafe_ptr) +static __always_inline int +bpf_probe_read_kernel_common(void *dst, u32 size, const void *unsafe_ptr, + const bool compat) { - int ret; + int ret = security_locked_down(LOCKDOWN_BPF_READ); - ret = security_locked_down(LOCKDOWN_BPF_READ); - if (ret < 0) + if (unlikely(ret < 0)) goto out; - - ret = probe_kernel_read(dst, unsafe_ptr, size); + 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) +{ + return bpf_probe_read_kernel_common(dst, size, unsafe_ptr, true); +} + +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_str_common(void *dst, u32 size, const void *unsafe_ptr, + const bool compat) +{ + int ret = security_locked_down(LOCKDOWN_BPF_READ); + + if (unlikely(ret < 0)) + goto out; + /* + * The strncpy_from_unsafe_*() 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_unsafe_strict(dst, unsafe_ptr, size); + if (unlikely(ret < 0)) +out: + memset(dst, 0, size); return ret; } -static const struct bpf_func_proto bpf_probe_read_proto = { - .func = bpf_probe_read, +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); +} + +static const struct bpf_func_proto bpf_probe_read_compat_str_proto = { + .func = bpf_probe_read_compat_str, .gpl_only = true, .ret_type = RET_INTEGER, .arg1_type = ARG_PTR_TO_UNINIT_MEM, @@ -583,41 +629,6 @@ static const struct bpf_func_proto bpf_current_task_under_cgroup_proto = { .arg2_type = ARG_ANYTHING, }; -BPF_CALL_3(bpf_probe_read_str, void *, dst, u32, size, - const void *, unsafe_ptr) -{ - int ret; - - ret = security_locked_down(LOCKDOWN_BPF_READ); - if (ret < 0) - goto out; - - /* - * The strncpy_from_unsafe() 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 = strncpy_from_unsafe(dst, unsafe_ptr, size); - if (unlikely(ret < 0)) -out: - memset(dst, 0, size); - - return ret; -} - -static const struct bpf_func_proto bpf_probe_read_str_proto = { - .func = bpf_probe_read_str, - .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, -}; - struct send_signal_irq_work { struct irq_work irq_work; struct task_struct *task; @@ -700,8 +711,6 @@ tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) return &bpf_map_pop_elem_proto; case BPF_FUNC_map_peek_elem: return &bpf_map_peek_elem_proto; - case BPF_FUNC_probe_read: - return &bpf_probe_read_proto; case BPF_FUNC_ktime_get_ns: return &bpf_ktime_get_ns_proto; case BPF_FUNC_tail_call: @@ -728,8 +737,10 @@ tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) return &bpf_current_task_under_cgroup_proto; case BPF_FUNC_get_prandom_u32: return &bpf_get_prandom_u32_proto; + case BPF_FUNC_probe_read: + return &bpf_probe_read_compat_proto; case BPF_FUNC_probe_read_str: - return &bpf_probe_read_str_proto; + return &bpf_probe_read_compat_str_proto; #ifdef CONFIG_CGROUPS case BPF_FUNC_get_current_cgroup_id: return &bpf_get_current_cgroup_id_proto; -- 2.40.1