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/user_events/example.c | 73 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 73 insertions(+) create mode 100644 samples/user_events/example.c (limited to 'samples/user_events/example.c') diff --git a/samples/user_events/example.c b/samples/user_events/example.c new file mode 100644 index 000000000..28165a096 --- /dev/null +++ b/samples/user_events/example.c @@ -0,0 +1,73 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (c) 2021, Microsoft Corporation. + * + * Authors: + * Beau Belgrave + */ + +#include +#include +#include +#include +#include +#include +#include +#include + +const char *data_file = "/sys/kernel/tracing/user_events_data"; +int enabled = 0; + +static int event_reg(int fd, const char *command, int *write, int *enabled) +{ + struct user_reg reg = {0}; + + reg.size = sizeof(reg); + reg.enable_bit = 31; + reg.enable_size = sizeof(*enabled); + reg.enable_addr = (__u64)enabled; + reg.name_args = (__u64)command; + + if (ioctl(fd, DIAG_IOCSREG, ®) == -1) + return -1; + + *write = reg.write_index; + + return 0; +} + +int main(int argc, char **argv) +{ + int data_fd, write; + struct iovec io[2]; + __u32 count = 0; + + data_fd = open(data_file, O_RDWR); + + if (event_reg(data_fd, "test u32 count", &write, &enabled) == -1) + return errno; + + /* Setup iovec */ + io[0].iov_base = &write; + io[0].iov_len = sizeof(write); + io[1].iov_base = &count; + io[1].iov_len = sizeof(count); +ask: + printf("Press enter to check status...\n"); + getchar(); + + /* Check if anyone is listening */ + if (enabled) { + /* Yep, trace out our data */ + writev(data_fd, (const struct iovec *)io, 2); + + /* Increase the count */ + count++; + + printf("Something was attached, wrote data\n"); + } + + goto ask; + + return 0; +} -- cgit v1.3.1