From 78004e9a87f240df03e2f73120d291763c32e0a7 Mon Sep 17 00:00:00 2001 From: Ali Ahmet Memis Date: Fri, 21 Aug 2026 01:45:27 +0000 Subject: openrisc: fix arbitrary kernel memory access via or1k_atomic syscall sys_or1k_atomic() (syscall 244 in the "or1k" ABI) takes two user pointers, v1 and v2, and swaps the words they point to in hand-written assembly. l.lwz r29,0(r4) l.lwz r27,0(r5) l.sw 0(r4),r27 l.sw 0(r5),r29 The pointers are not checked with access_ok(). The four memory accesses also have no exception table entries. A caller passes a kernel address as either pointer, and the syscall reads from and writes to it directly. This gives an unprivileged process a kernel read/write primitive. It overwrites kernel data such as the sys_call_table, gaining code execution in kernel context. Check both pointers before entering the critical section. Add fixups for the four memory accesses so faults on valid but unmapped user addresses return -EFAULT. [shorne@gmail.com: fix comment style] Fixes: 9d02a4283e9c ("OpenRISC: Boot code") Cc: stable@vger.kernel.org Signed-off-by: Ali Ahmet Memis Signed-off-by: Stafford Horne --- arch/x86/boot/cmdline.c | 156 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 156 insertions(+) create mode 100644 arch/x86/boot/cmdline.c (limited to 'arch/x86/boot/cmdline.c') diff --git a/arch/x86/boot/cmdline.c b/arch/x86/boot/cmdline.c new file mode 100644 index 000000000..21d56ae83 --- /dev/null +++ b/arch/x86/boot/cmdline.c @@ -0,0 +1,156 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* -*- linux-c -*- ------------------------------------------------------- * + * + * Copyright (C) 1991, 1992 Linus Torvalds + * Copyright 2007 rPath, Inc. - All Rights Reserved + * + * ----------------------------------------------------------------------- */ + +/* + * Simple command-line parser for early boot. + */ + +#include "boot.h" + +static inline int myisspace(u8 c) +{ + return c <= ' '; /* Close enough approximation */ +} + +/* + * Find a non-boolean option, that is, "option=argument". In accordance + * with standard Linux practice, if this option is repeated, this returns + * the last instance on the command line. + * + * Returns the length of the argument (regardless of if it was + * truncated to fit in the buffer), or -1 on not found. + */ +int __cmdline_find_option(unsigned long cmdline_ptr, const char *option, char *buffer, int bufsize) +{ + addr_t cptr; + char c; + int len = -1; + const char *opptr = NULL; + char *bufptr = buffer; + enum { + st_wordstart, /* Start of word/after whitespace */ + st_wordcmp, /* Comparing this word */ + st_wordskip, /* Miscompare, skip */ + st_bufcpy /* Copying this to buffer */ + } state = st_wordstart; + + if (!cmdline_ptr) + return -1; /* No command line */ + + cptr = cmdline_ptr & 0xf; + set_fs(cmdline_ptr >> 4); + + while (cptr < 0x10000 && (c = rdfs8(cptr++))) { + switch (state) { + case st_wordstart: + if (myisspace(c)) + break; + + /* else */ + state = st_wordcmp; + opptr = option; + fallthrough; + + case st_wordcmp: + if (c == '=' && !*opptr) { + len = 0; + bufptr = buffer; + state = st_bufcpy; + } else if (myisspace(c)) { + state = st_wordstart; + } else if (c != *opptr++) { + state = st_wordskip; + } + break; + + case st_wordskip: + if (myisspace(c)) + state = st_wordstart; + break; + + case st_bufcpy: + if (myisspace(c)) { + state = st_wordstart; + } else { + if (len < bufsize-1) + *bufptr++ = c; + len++; + } + break; + } + } + + if (bufsize) + *bufptr = '\0'; + + return len; +} + +/* + * Find a boolean option (like quiet,noapic,nosmp....) + * + * Returns the position of that option (starts counting with 1) + * or 0 on not found + */ +int __cmdline_find_option_bool(unsigned long cmdline_ptr, const char *option) +{ + addr_t cptr; + char c; + int pos = 0, wstart = 0; + const char *opptr = NULL; + enum { + st_wordstart, /* Start of word/after whitespace */ + st_wordcmp, /* Comparing this word */ + st_wordskip, /* Miscompare, skip */ + } state = st_wordstart; + + if (!cmdline_ptr) + return -1; /* No command line */ + + cptr = cmdline_ptr & 0xf; + set_fs(cmdline_ptr >> 4); + + while (cptr < 0x10000) { + c = rdfs8(cptr++); + pos++; + + switch (state) { + case st_wordstart: + if (!c) + return 0; + else if (myisspace(c)) + break; + + state = st_wordcmp; + opptr = option; + wstart = pos; + fallthrough; + + case st_wordcmp: + if (!*opptr) + if (!c || myisspace(c)) + return wstart; + else + state = st_wordskip; + else if (!c) + return 0; + else if (c != *opptr++) + state = st_wordskip; + break; + + case st_wordskip: + if (!c) + return 0; + else if (myisspace(c)) + state = st_wordstart; + break; + } + } + + return 0; /* Buffer overrun */ +} -- cgit v1.3.1