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Revision da353fac65fede6b8b4cfe207f0d9408e3121105 authored by Daniel Jordan on 27 October 2021, 21:59:20 UTC, committed by David S. Miller on 28 October 2021, 13:41:20 UTC 
net/tls: Fix flipped sign in tls_err_abort() calls
 
sk->sk_err appears to expect a positive value, a convention that ktls
doesn't always follow and that leads to memory corruption in other code.
For instance,

    [kworker]
    tls_encrypt_done(..., err=<negative error from crypto request>)
      tls_err_abort(.., err)
        sk->sk_err = err;

    [task]
    splice_from_pipe_feed
      ...
        tls_sw_do_sendpage
          if (sk->sk_err) {
            ret = -sk->sk_err;  // ret is positive

    splice_from_pipe_feed (continued)
      ret = actor(...)  // ret is still positive and interpreted as bytes
                        // written, resulting in underflow of buf->len and
                        // sd->len, leading to huge buf->offset and bogus
                        // addresses computed in later calls to actor()

Fix all tls_err_abort() callers to pass a negative error code
consistently and centralize the error-prone sign flip there, throwing in
a warning to catch future misuse and uninlining the function so it
really does only warn once.

Cc: stable@vger.kernel.org
Fixes: c46234ebb4d1e ("tls: RX path for ktls")
Reported-by: syzbot+b187b77c8474f9648fae@syzkaller.appspotmail.com
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
1 parent a32f07d
Raw File
tracex5_user.c 
// SPDX-License-Identifier: GPL-2.0
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <linux/filter.h>
#include <linux/seccomp.h>
#include <sys/prctl.h>
#include <bpf/bpf.h>
#include <bpf/libbpf.h>
#include <sys/resource.h>
#include "trace_helpers.h"

#ifdef __mips__
#define	MAX_ENTRIES  6000 /* MIPS n64 syscalls start at 5000 */
#else
#define	MAX_ENTRIES  1024
#endif

/* install fake seccomp program to enable seccomp code path inside the kernel,
 * so that our kprobe attached to seccomp_phase1() can be triggered
 */
static void install_accept_all_seccomp(void)
{
	struct sock_filter filter[] = {
		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
	};
	struct sock_fprog prog = {
		.len = (unsigned short)(sizeof(filter)/sizeof(filter[0])),
		.filter = filter,
	};
	if (prctl(PR_SET_SECCOMP, 2, &prog))
		perror("prctl");
}

int main(int ac, char **argv)
{
	struct bpf_link *link = NULL;
	struct bpf_program *prog;
	struct bpf_object *obj;
	int key, fd, progs_fd;
	const char *section;
	char filename[256];
	FILE *f;

	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
	obj = bpf_object__open_file(filename, NULL);
	if (libbpf_get_error(obj)) {
		fprintf(stderr, "ERROR: opening BPF object file failed\n");
		return 0;
	}

	prog = bpf_object__find_program_by_name(obj, "bpf_prog1");
	if (!prog) {
		printf("finding a prog in obj file failed\n");
		goto cleanup;
	}

	/* load BPF program */
	if (bpf_object__load(obj)) {
		fprintf(stderr, "ERROR: loading BPF object file failed\n");
		goto cleanup;
	}

	link = bpf_program__attach(prog);
	if (libbpf_get_error(link)) {
		fprintf(stderr, "ERROR: bpf_program__attach failed\n");
		link = NULL;
		goto cleanup;
	}

	progs_fd = bpf_object__find_map_fd_by_name(obj, "progs");
	if (progs_fd < 0) {
		fprintf(stderr, "ERROR: finding a map in obj file failed\n");
		goto cleanup;
	}

	bpf_object__for_each_program(prog, obj) {
		section = bpf_program__section_name(prog);
		/* register only syscalls to PROG_ARRAY */
		if (sscanf(section, "kprobe/%d", &key) != 1)
			continue;

		fd = bpf_program__fd(prog);
		bpf_map_update_elem(progs_fd, &key, &fd, BPF_ANY);
	}

	install_accept_all_seccomp();

	f = popen("dd if=/dev/zero of=/dev/null count=5", "r");
	(void) f;

	read_trace_pipe();

cleanup:
	bpf_link__destroy(link);
	bpf_object__close(obj);
	return 0;
}
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