Revision d29bd41428cfff9b582c248db14a47e2be8457a8 authored by Paolo Valente on 15 October 2021, 14:43:36 UTC, committed by Jens Axboe on 17 October 2021, 13:03:02 UTC
Since commit 430a67f9d616 ("block, bfq: merge bursts of newly-created queues"), BFQ maintains a per-group pointer to the last bfq_queue created. If such a queue, say bfqq, happens to move to a different group, then bfqq is no more a valid last bfq_queue created for its previous group. That pointer must then be cleared. Not resetting such a pointer may also cause UAF, if bfqq happens to also be freed after being moved to a different group. This commit performs this missing reset. As such it fixes commit 430a67f9d616 ("block, bfq: merge bursts of newly-created queues"). Such a missing reset is most likely the cause of the crash reported in [1]. With some analysis, we found that this crash was due to the above UAF. And such UAF did go away with this commit applied [1]. Anyway, before this commit, that crash happened to be triggered in conjunction with commit 2d52c58b9c9b ("block, bfq: honor already-setup queue merges"). The latter was then reverted by commit ebc69e897e17 ("Revert "block, bfq: honor already-setup queue merges""). Yet commit 2d52c58b9c9b ("block, bfq: honor already-setup queue merges") contains no error related with the above UAF, and can then be restored. [1] https://bugzilla.kernel.org/show_bug.cgi?id=214503 Fixes: 430a67f9d616 ("block, bfq: merge bursts of newly-created queues") Tested-by: Grzegorz Kowal <custos.mentis@gmail.com> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Link: https://lore.kernel.org/r/20211015144336.45894-2-paolo.valente@linaro.org Signed-off-by: Jens Axboe <axboe@kernel.dk>
1 parent a204176
extable.c
// SPDX-License-Identifier: GPL-2.0-or-later
/* Rewritten by Rusty Russell, on the backs of many others...
Copyright (C) 2001 Rusty Russell, 2002 Rusty Russell IBM.
*/
#include <linux/ftrace.h>
#include <linux/memory.h>
#include <linux/extable.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/init.h>
#include <linux/kprobes.h>
#include <linux/filter.h>
#include <asm/sections.h>
#include <linux/uaccess.h>
/*
* mutex protecting text section modification (dynamic code patching).
* some users need to sleep (allocating memory...) while they hold this lock.
*
* Note: Also protects SMP-alternatives modification on x86.
*
* NOT exported to modules - patching kernel text is a really delicate matter.
*/
DEFINE_MUTEX(text_mutex);
extern struct exception_table_entry __start___ex_table[];
extern struct exception_table_entry __stop___ex_table[];
/* Cleared by build time tools if the table is already sorted. */
u32 __initdata __visible main_extable_sort_needed = 1;
/* Sort the kernel's built-in exception table */
void __init sort_main_extable(void)
{
if (main_extable_sort_needed &&
&__stop___ex_table > &__start___ex_table) {
pr_notice("Sorting __ex_table...\n");
sort_extable(__start___ex_table, __stop___ex_table);
}
}
/* Given an address, look for it in the kernel exception table */
const
struct exception_table_entry *search_kernel_exception_table(unsigned long addr)
{
return search_extable(__start___ex_table,
__stop___ex_table - __start___ex_table, addr);
}
/* Given an address, look for it in the exception tables. */
const struct exception_table_entry *search_exception_tables(unsigned long addr)
{
const struct exception_table_entry *e;
e = search_kernel_exception_table(addr);
if (!e)
e = search_module_extables(addr);
if (!e)
e = search_bpf_extables(addr);
return e;
}
int init_kernel_text(unsigned long addr)
{
if (addr >= (unsigned long)_sinittext &&
addr < (unsigned long)_einittext)
return 1;
return 0;
}
int notrace core_kernel_text(unsigned long addr)
{
if (addr >= (unsigned long)_stext &&
addr < (unsigned long)_etext)
return 1;
if (system_state < SYSTEM_RUNNING &&
init_kernel_text(addr))
return 1;
return 0;
}
/**
* core_kernel_data - tell if addr points to kernel data
* @addr: address to test
*
* Returns true if @addr passed in is from the core kernel data
* section.
*
* Note: On some archs it may return true for core RODATA, and false
* for others. But will always be true for core RW data.
*/
int core_kernel_data(unsigned long addr)
{
if (addr >= (unsigned long)_sdata &&
addr < (unsigned long)_edata)
return 1;
return 0;
}
int __kernel_text_address(unsigned long addr)
{
if (kernel_text_address(addr))
return 1;
/*
* There might be init symbols in saved stacktraces.
* Give those symbols a chance to be printed in
* backtraces (such as lockdep traces).
*
* Since we are after the module-symbols check, there's
* no danger of address overlap:
*/
if (init_kernel_text(addr))
return 1;
return 0;
}
int kernel_text_address(unsigned long addr)
{
bool no_rcu;
int ret = 1;
if (core_kernel_text(addr))
return 1;
/*
* If a stack dump happens while RCU is not watching, then
* RCU needs to be notified that it requires to start
* watching again. This can happen either by tracing that
* triggers a stack trace, or a WARN() that happens during
* coming back from idle, or cpu on or offlining.
*
* is_module_text_address() as well as the kprobe slots,
* is_bpf_text_address() and is_bpf_image_address require
* RCU to be watching.
*/
no_rcu = !rcu_is_watching();
/* Treat this like an NMI as it can happen anywhere */
if (no_rcu)
rcu_nmi_enter();
if (is_module_text_address(addr))
goto out;
if (is_ftrace_trampoline(addr))
goto out;
if (is_kprobe_optinsn_slot(addr) || is_kprobe_insn_slot(addr))
goto out;
if (is_bpf_text_address(addr))
goto out;
ret = 0;
out:
if (no_rcu)
rcu_nmi_exit();
return ret;
}
/*
* On some architectures (PPC64, IA64) function pointers
* are actually only tokens to some data that then holds the
* real function address. As a result, to find if a function
* pointer is part of the kernel text, we need to do some
* special dereferencing first.
*/
int func_ptr_is_kernel_text(void *ptr)
{
unsigned long addr;
addr = (unsigned long) dereference_function_descriptor(ptr);
if (core_kernel_text(addr))
return 1;
return is_module_text_address(addr);
}
![swh spinner](/static/img/swh-spinner.gif)
Computing file changes ...