From 33a154a96e71a34a1bcca9f40da343dbbf7b38b4 Mon Sep 17 00:00:00 2001 From: Alexei Starovoitov Date: Thu, 1 Oct 2026 14:52:55 +0000 Subject: selftests/bpf: Test packet range of pointers sharing an id Add tests where two packet pointers share an id and tightening one pointer's umax from its var_off would put it less than their constant distance from the other's umax: with an index & 0x38 capped at 50, the base pointer keeps umax 50, so the pointer 8 bytes further on must keep umax 58, even though its known bits allow at most 56. These refused a valid program or accepted an out-of-bounds access before the fix: - check the advanced copy, load through the base: valid, was refused; - check the base, load the byte at base + 1 through a copy advanced by 8: was accepted; - check base + 4, load 4 bytes at base + 2 through base + 8: reads two bytes past the checked range, was accepted; - the same as the second with data_meta pointers checked against data: was accepted. These pass with and without the fix and cover nearby paths: - subtract an unknown scalar from a checked pointer and load below it (the range is kept across a new id); - reach a load through two paths whose checks cover 8 and 7 bytes after the loaded pointer; the second path must not be pruned by the first; - spill a copy of a pointer, check the pointer, fill the copy and load one byte past the checked range: the load is refused, and the copy has the range of the check. Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20261001145255.855630-2-alexei.starovoitov@gmail.com Signed-off-by: Kumar Kartikeya Dwivedi --- samples/pidfd/.gitignore | 2 + samples/pidfd/Makefile | 4 ++ samples/pidfd/pidfd-metadata.c | 120 +++++++++++++++++++++++++++++++++++++++++ 3 files changed, 126 insertions(+) create mode 100644 samples/pidfd/.gitignore create mode 100644 samples/pidfd/Makefile create mode 100644 samples/pidfd/pidfd-metadata.c (limited to 'samples/pidfd') diff --git a/samples/pidfd/.gitignore b/samples/pidfd/.gitignore new file mode 100644 index 000000000..d4cfa3176 --- /dev/null +++ b/samples/pidfd/.gitignore @@ -0,0 +1,2 @@ +# SPDX-License-Identifier: GPL-2.0-only +/pidfd-metadata diff --git a/samples/pidfd/Makefile b/samples/pidfd/Makefile new file mode 100644 index 000000000..9754e2d81 --- /dev/null +++ b/samples/pidfd/Makefile @@ -0,0 +1,4 @@ +# SPDX-License-Identifier: GPL-2.0 +usertprogs-always-y += pidfd-metadata + +userccflags += -I usr/include diff --git a/samples/pidfd/pidfd-metadata.c b/samples/pidfd/pidfd-metadata.c new file mode 100644 index 000000000..c459155da --- /dev/null +++ b/samples/pidfd/pidfd-metadata.c @@ -0,0 +1,120 @@ +// SPDX-License-Identifier: GPL-2.0 + +#define _GNU_SOURCE +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#ifndef CLONE_PIDFD +#define CLONE_PIDFD 0x00001000 +#endif + +#ifndef __NR_pidfd_send_signal +#define __NR_pidfd_send_signal -1 +#endif + +static int do_child(void *args) +{ + printf("%d\n", getpid()); + _exit(EXIT_SUCCESS); +} + +static pid_t pidfd_clone(int flags, int *pidfd) +{ + size_t stack_size = 1024; + char *stack[1024] = { 0 }; + +#ifdef __ia64__ + return __clone2(do_child, stack, stack_size, flags | SIGCHLD, NULL, pidfd); +#else + return clone(do_child, stack + stack_size, flags | SIGCHLD, NULL, pidfd); +#endif +} + +static inline int sys_pidfd_send_signal(int pidfd, int sig, siginfo_t *info, + unsigned int flags) +{ + return syscall(__NR_pidfd_send_signal, pidfd, sig, info, flags); +} + +static int pidfd_metadata_fd(pid_t pid, int pidfd) +{ + int procfd, ret; + char path[100]; + + snprintf(path, sizeof(path), "/proc/%d", pid); + procfd = open(path, O_DIRECTORY | O_RDONLY | O_CLOEXEC); + if (procfd < 0) { + warn("Failed to open %s\n", path); + return -1; + } + + /* + * Verify that the pid has not been recycled and our /proc/ handle + * is still valid. + */ + ret = sys_pidfd_send_signal(pidfd, 0, NULL, 0); + if (ret < 0) { + switch (errno) { + case EPERM: + /* Process exists, just not allowed to signal it. */ + break; + default: + warn("Failed to signal process\n"); + close(procfd); + procfd = -1; + } + } + + return procfd; +} + +int main(int argc, char *argv[]) +{ + int pidfd = -1, ret = EXIT_FAILURE; + char buf[4096] = { 0 }; + pid_t pid; + int procfd, statusfd; + ssize_t bytes; + + pid = pidfd_clone(CLONE_PIDFD, &pidfd); + if (pid < 0) + err(ret, "CLONE_PIDFD"); + if (pidfd == -1) { + warnx("CLONE_PIDFD is not supported by the kernel"); + goto out; + } + + procfd = pidfd_metadata_fd(pid, pidfd); + close(pidfd); + if (procfd < 0) + goto out; + + statusfd = openat(procfd, "status", O_RDONLY | O_CLOEXEC); + close(procfd); + if (statusfd < 0) + goto out; + + bytes = read(statusfd, buf, sizeof(buf)); + if (bytes > 0) + bytes = write(STDOUT_FILENO, buf, bytes); + close(statusfd); + ret = EXIT_SUCCESS; + +out: + (void)wait(NULL); + + exit(ret); +} -- cgit v1.3.1