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b=iZBugpeWHZBpl3K2H5FfQFyfR7ntEyxjCFA1kK9LPwmn4G5bzK+4DC+yiFQ0k+A7U Fdi7kcXKaE3PMxeTqP3OuQNGjVQCRlkCZdMyn1KdwQzm1DYOsEqUgysdVghIMkzJgX V540OL3D8fAqoQtdoDKhc5wICR6Jz6CKlhUmtt3SKdJmXFJxvC0qH8LBRQBLd7c0Yf pTurnBSWRhT6PpSMTNOs7p272p5H+yj3rmIGpz5CJdDKSWT0twSCZVpjoA6LTm9MnM GvadEMH+/YEHnYObRILTmkZwqr7ierJJospjmIxN+Izz56l5bWiog85uUZUfWxVdU3 7mTphYnGVSdzw== From: Jiri Olsa To: Alexei Starovoitov , Daniel Borkmann Cc: bpf@vger.kernel.org, linux-mm@kvack.org, Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Lorenzo Stoakes , John Fastabend , Federico Di Pierro Subject: [PATCH bpf-next 7/8] selftests/bpf: Test bpf_copy_to_user kfunc Date: Thu, 29 Oct 2026 22:25:50 +0100 Message-ID: <20261029212551.56964-8-jolsa@kernel.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261029212551.56964-1-jolsa@kernel.org> References: <20261029212551.56964-1-jolsa@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 32A5340004 X-Stat-Signature: b611ah4pc1dsjbn9guohyczmac8qz7yx X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Rspam-User: X-HE-Tag: 1793309228-641544 X-HE-Meta: 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 4Jf+A1WR V/v4NNrRRLfkM2lSvJg4lkUIlGYLRSXrDPk7Ylb2zr+h0gDgL7oZ+za71BrvhAcSM78Y2ZGtv6jjNYz/XV2awcWkDptDnMj1UmazqXHSteFi/CjeWRlS+dw7Ac+SDZsYHPGCfNIycqQqg4ffohjvFDjbKU8szCjWwHlS5z3MvysZYMQbB4WUa5T43bGlM2voc7zhcMUv7F+ten2e0r46cA0iq+hTbN3WIh07IKXJZWt5jdvYn3ujxhuTjYGBhraJUK0etqVwimZiEid308SHCtqtQP1CTFavxgrqFXytKX2cEbAagKfetfJ36ksbCaizPKaaNhxEc76duWhYhcoJAKBkpkBRuf0vJ+2Y42OCOavcqbxp8uWaMexPrHsF/UNUvvqQ3 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 Test that bpf_copy_to_user can fault in a paged-out page and write to a read-only mapping. Also verify that a partial copy crossing into an unmapped page returns -EFAULT while leaving the copied byte in place. Assisted-by: Codex:GPT-6 Signed-off-by: Jiri Olsa --- .../selftests/bpf/prog_tests/user_mem.c | 106 ++++++++++++++++++ tools/testing/selftests/bpf/progs/user_mem.c | 17 +++ 2 files changed, 123 insertions(+) diff --git a/tools/testing/selftests/bpf/prog_tests/user_mem.c b/tools/testing/selftests/bpf/prog_tests/user_mem.c index 7fa827298d24..c87620e39abb 100644 --- a/tools/testing/selftests/bpf/prog_tests/user_mem.c +++ b/tools/testing/selftests/bpf/prog_tests/user_mem.c @@ -12,8 +12,11 @@ enum { USER_MEM_MMAP = 1, USER_MEM_UNMAP, USER_MEM_COPY_INSNS, + USER_MEM_COPY, }; +static const char data[] = "fault-enabled BPF write"; + static noinline void user_mem_trigger(void) { asm volatile ("" ::: "memory"); @@ -102,6 +105,18 @@ static bool user_mem_copy_insns(struct user_mem *skel, unsigned long addr) return ASSERT_OK(skel->bss->ret, "user_write"); } +static int user_mem_copy(struct user_mem *skel, unsigned long addr, + u32 size, u64 flags) +{ + skel->bss->user_addr = addr; + skel->bss->copy_size = size; + skel->bss->copy_flags = flags; + skel->bss->action = USER_MEM_COPY; + user_mem_trigger(); + + return skel->bss->ret; +} + static void test_execute_user_page(struct user_mem *skel) { long page_size = sysconf(_SC_PAGESIZE); @@ -163,6 +178,91 @@ static void test_partial_exec(struct user_mem *skel) munmap((void *)addr, page_size * 3); } +static void test_faultable_write(struct user_mem *skel) +{ + long page_size = sysconf(_SC_PAGESIZE); + unsigned long addr = ~0UL; + unsigned char vec; + int i; + + if (!user_mem_mmap(skel, page_size, PROT_READ | PROT_WRITE, &addr)) + return; + + /* Make sure there is a private resident page to page out. */ + memset((void *)addr, 0, page_size); + + /* Retry pageout until mincore confirms that the page is no longer resident. */ + for (i = 0; i < 500; i++) { + if (madvise((void *)addr, page_size, MADV_PAGEOUT)) { + test__skip(); + goto out; + } + if (!ASSERT_OK(mincore((void *)addr, page_size, &vec), "mincore")) + goto out; + if (!(vec & 1)) + break; + usleep(100); + } + if (i == 500) { + test__skip(); + goto out; + } + + /* ..and do the copy to it. */ + if (!ASSERT_OK(user_mem_copy(skel, addr, sizeof(data), 0), "user_write_data")) + goto out; + + ASSERT_EQ(memcmp((void *)addr, data, sizeof(data)), 0, "written_data"); + +out: + if (addr != ~0UL) + munmap((void *)addr, page_size); +} + +static void test_copy_to_readonly_mapping(struct user_mem *skel) +{ + long page_size = sysconf(_SC_PAGESIZE); + unsigned long addr = ~0UL; + + if (!user_mem_mmap(skel, page_size, PROT_READ, &addr)) + return; + + /* Assert we can copy to read-only mapping. */ + if (!ASSERT_OK(user_mem_copy(skel, addr, sizeof(data), 0), "readonly_copy")) + goto out; + + ASSERT_EQ(memcmp((void *)addr, data, sizeof(data)), 0, "readonly_copy_data"); + +out: + if (addr != ~0UL) + munmap((void *)addr, page_size); +} + +static void test_partial_copy_fault(struct user_mem *skel) +{ + long page_size = sysconf(_SC_PAGESIZE); + bool second_page_unmapped = false; + unsigned long addr = ~0UL; + + if (!user_mem_mmap(skel, page_size * 2, PROT_READ | PROT_WRITE, &addr)) + return; + + if (!user_mem_munmap(skel, addr + page_size, page_size)) + goto out; + + second_page_unmapped = true; + + ASSERT_EQ(user_mem_copy(skel, addr + page_size - 1, sizeof(data), 0), + -EFAULT, "partial_copy"); + + /* The byte before the fault stays written. */ + ASSERT_EQ(((char *)addr)[page_size - 1], 'f', "partial_copy_data"); + +out: + if (addr != ~0UL) + munmap((void *)addr, second_page_unmapped ? page_size : page_size * 2); +} + void test_user_mem(void) { struct user_mem *skel; @@ -181,6 +281,12 @@ void test_user_mem(void) test_execute_user_page(skel); if (test__start_subtest("partial_exec")) test_partial_exec(skel); + if (test__start_subtest("faultable_write")) + test_faultable_write(skel); + if (test__start_subtest("copy_to_readonly_mapping")) + test_copy_to_readonly_mapping(skel); + if (test__start_subtest("partial_copy_fault")) + test_partial_copy_fault(skel); out: user_mem__destroy(skel); diff --git a/tools/testing/selftests/bpf/progs/user_mem.c b/tools/testing/selftests/bpf/progs/user_mem.c index b477132e3883..6ebfdc54edad 100644 --- a/tools/testing/selftests/bpf/progs/user_mem.c +++ b/tools/testing/selftests/bpf/progs/user_mem.c @@ -17,6 +17,7 @@ enum { USER_MEM_MMAP = 1, USER_MEM_UNMAP, USER_MEM_COPY_INSNS, + USER_MEM_COPY, }; int monitored_pid; @@ -27,6 +28,9 @@ unsigned long user_addr; unsigned long map_len; unsigned long map_prot; +u64 copy_flags; +u32 copy_size; + #if defined(__TARGET_ARCH_x86) static const unsigned char insns[] = { 0xf3, 0x0f, 0x1e, 0xfa, /* endbr64 */ @@ -43,9 +47,13 @@ static const unsigned char insns[] = { static const unsigned char insns[] = { 0 }; #endif +static const char data[] = "fault-enabled BPF write"; + SEC("uprobe.s//proc/self/exe:user_mem_trigger") int user_mem_test(struct pt_regs *ctx) { + u32 size; + if ((bpf_get_current_pid_tgid() >> 32) != monitored_pid) return 0; @@ -59,6 +67,15 @@ int user_mem_test(struct pt_regs *ctx) case USER_MEM_COPY_INSNS: ret = bpf_copy_to_user((void *)user_addr, insns, sizeof(insns), 0); break; + case USER_MEM_COPY: + /* Bound the kfunc length using a local copy of copy_size. */ + size = copy_size; + if (size > sizeof(data)) { + ret = -22; /* -EINVAL */ + break; + } + ret = bpf_copy_to_user((void *)user_addr, data, size, copy_flags); + break; } return 0; -- 2.54.0