staging: rtl8723bs: fix OOB read in rtw_action_frame_parse()grafted

rtw_action_frame_parse() takes a frame_len parameter but never
actually checks it before indexing into the frame body:

	const u8 *frame_body = frame + sizeof(struct ieee80211_hdr_3addr);
	...
	c = frame_body[0];
	...
	a = frame_body[1];

frame_body already points 24 bytes (sizeof(struct
ieee80211_hdr_3addr)) into frame, so reading frame_body[0] and
frame_body[1] requires frame_len >= 26. A management action frame
shorter than that (e.g. exactly 24 bytes, the minimum a malicious
peer can send) causes a 1-2 byte out-of-bounds read.

This is reachable from rtw_cfg80211_monitor_if_xmit_entry() and
cfg80211_rtw_mgmt_tx() in ioctl_cfg80211.c, both of which pass
attacker/user-influenced frame buffers and lengths straight through.

Add the missing length check before frame_body is dereferenced.

Fixes: 554c0a3abf216 ("staging: Add rtl8723bs sdio wifi driver")
Cc: stable@vger.kernel.org
Signed-off-by: Muhammad Bilal <meatuni001@gmail.com>
Link: https://patch.msgid.link/20260728125456.32359-3-meatuni001@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 191 insertions, 0 deletions

diff --git a/samples/seccomp/bpf-direct.c b/samples/seccomp/bpf-direct.c
new file mode 100644
index 000000000..c09e4a17a
--- /dev/null
+++ b/samples/seccomp/bpf-direct.c
@@ -0,0 +1,191 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Seccomp filter example for x86 (32-bit and 64-bit) with BPF macros
+ *
+ * Copyright (c) 2012 The Chromium OS Authors <chromium-os-dev@chromium.org>
+ * Author: Will Drewry <wad@chromium.org>
+ *
+ * The code may be used by anyone for any purpose,
+ * and can serve as a starting point for developing
+ * applications using prctl(PR_SET_SECCOMP, 2, ...).
+ */
+#if defined(__i386__) || defined(__x86_64__)
+#define SUPPORTED_ARCH 1
+#endif
+
+#if defined(SUPPORTED_ARCH)
+#define __USE_GNU 1
+#define _GNU_SOURCE 1
+
+#include <linux/types.h>
+#include <linux/filter.h>
+#include <linux/seccomp.h>
+#include <linux/unistd.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stddef.h>
+#include <string.h>
+#include <sys/prctl.h>
+#include <unistd.h>
+
+#define syscall_arg(_n) (offsetof(struct seccomp_data, args[_n]))
+#define syscall_nr (offsetof(struct seccomp_data, nr))
+
+#if defined(__i386__)
+#define REG_RESULT	REG_EAX
+#define REG_SYSCALL	REG_EAX
+#define REG_ARG0	REG_EBX
+#define REG_ARG1	REG_ECX
+#define REG_ARG2	REG_EDX
+#define REG_ARG3	REG_ESI
+#define REG_ARG4	REG_EDI
+#define REG_ARG5	REG_EBP
+#elif defined(__x86_64__)
+#define REG_RESULT	REG_RAX
+#define REG_SYSCALL	REG_RAX
+#define REG_ARG0	REG_RDI
+#define REG_ARG1	REG_RSI
+#define REG_ARG2	REG_RDX
+#define REG_ARG3	REG_R10
+#define REG_ARG4	REG_R8
+#define REG_ARG5	REG_R9
+#endif
+
+#ifndef PR_SET_NO_NEW_PRIVS
+#define PR_SET_NO_NEW_PRIVS 38
+#endif
+
+#ifndef SYS_SECCOMP
+#define SYS_SECCOMP 1
+#endif
+
+static void emulator(int nr, siginfo_t *info, void *void_context)
+{
+	ucontext_t *ctx = (ucontext_t *)(void_context);
+	int syscall;
+	char *buf;
+	ssize_t bytes;
+	size_t len;
+	if (info->si_code != SYS_SECCOMP)
+		return;
+	if (!ctx)
+		return;
+	syscall = ctx->uc_mcontext.gregs[REG_SYSCALL];
+	buf = (char *) ctx->uc_mcontext.gregs[REG_ARG1];
+	len = (size_t) ctx->uc_mcontext.gregs[REG_ARG2];
+
+	if (syscall != __NR_write)
+		return;
+	if (ctx->uc_mcontext.gregs[REG_ARG0] != STDERR_FILENO)
+		return;
+	/* Redirect stderr messages to stdout. Doesn't handle EINTR, etc */
+	ctx->uc_mcontext.gregs[REG_RESULT] = -1;
+	if (write(STDOUT_FILENO, "[ERR] ", 6) > 0) {
+		bytes = write(STDOUT_FILENO, buf, len);
+		ctx->uc_mcontext.gregs[REG_RESULT] = bytes;
+	}
+	return;
+}
+
+static int install_emulator(void)
+{
+	struct sigaction act;
+	sigset_t mask;
+	memset(&act, 0, sizeof(act));
+	sigemptyset(&mask);
+	sigaddset(&mask, SIGSYS);
+
+	act.sa_sigaction = &emulator;
+	act.sa_flags = SA_SIGINFO;
+	if (sigaction(SIGSYS, &act, NULL) < 0) {
+		perror("sigaction");
+		return -1;
+	}
+	if (sigprocmask(SIG_UNBLOCK, &mask, NULL)) {
+		perror("sigprocmask");
+		return -1;
+	}
+	return 0;
+}
+
+static int install_filter(void)
+{
+	struct sock_filter filter[] = {
+		/* Grab the system call number */
+		BPF_STMT(BPF_LD+BPF_W+BPF_ABS, syscall_nr),
+		/* Jump table for the allowed syscalls */
+		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_rt_sigreturn, 0, 1),
+		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
+#ifdef __NR_sigreturn
+		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_sigreturn, 0, 1),
+		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
+#endif
+		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_exit_group, 0, 1),
+		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
+		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_exit, 0, 1),
+		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
+		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_read, 1, 0),
+		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_write, 3, 2),
+
+		/* Check that read is only using stdin. */
+		BPF_STMT(BPF_LD+BPF_W+BPF_ABS, syscall_arg(0)),
+		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, STDIN_FILENO, 4, 0),
+		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_KILL),
+
+		/* Check that write is only using stdout */
+		BPF_STMT(BPF_LD+BPF_W+BPF_ABS, syscall_arg(0)),
+		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, STDOUT_FILENO, 1, 0),
+		/* Trap attempts to write to stderr */
+		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, STDERR_FILENO, 1, 2),
+
+		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
+		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_TRAP),
+		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_KILL),
+	};
+	struct sock_fprog prog = {
+		.len = (unsigned short)(sizeof(filter)/sizeof(filter[0])),
+		.filter = filter,
+	};
+
+	if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
+		perror("prctl(NO_NEW_PRIVS)");
+		return 1;
+	}
+
+
+	if (prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog)) {
+		perror("prctl");
+		return 1;
+	}
+	return 0;
+}
+
+#define payload(_c) (_c), sizeof((_c))
+int main(int argc, char **argv)
+{
+	char buf[4096];
+	ssize_t bytes = 0;
+	if (install_emulator())
+		return 1;
+	if (install_filter())
+		return 1;
+	syscall(__NR_write, STDOUT_FILENO,
+		payload("OHAI! WHAT IS YOUR NAME? "));
+	bytes = syscall(__NR_read, STDIN_FILENO, buf, sizeof(buf));
+	syscall(__NR_write, STDOUT_FILENO, payload("HELLO, "));
+	syscall(__NR_write, STDOUT_FILENO, buf, bytes);
+	syscall(__NR_write, STDERR_FILENO,
+		payload("Error message going to STDERR\n"));
+	return 0;
+}
+#else	/* SUPPORTED_ARCH */
+/*
+ * This sample is x86-only.  Since kernel samples are compiled with the
+ * host toolchain, a non-x86 host will result in using only the main()
+ * below.
+ */
+int main(void)
+{
+	return 1;
+}
+#endif	/* SUPPORTED_ARCH */