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module: Fix livepatch/ftrace module text permissions race
It's possible for livepatch and ftrace to be toggling a module's text
permissions at the same time, resulting in the following panic:
BUG: unable to handle page fault for address: ffffffffc005b1d9
#PF: supervisor write access in kernel mode
#PF: error_code(0x0003) - permissions violation
PGD 3ea0c067 P4D 3ea0c067 PUD 3ea0e067 PMD 3cc13067 PTE 3b8a1061
Oops: 0003 [#1] PREEMPT SMP PTI
CPU: 1 PID: 453 Comm: insmod Tainted: G O K 5.2.0-rc1-a188339ca5 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-20181126_142135-anatol 04/01/2014
RIP: 0010:apply_relocate_add+0xbe/0x14c
Code: fa 0b 74 21 48 83 fa 18 74 38 48 83 fa 0a 75 40 eb 08 48 83 38 00 74 33 eb 53 83 38 00 75 4e 89 08 89 c8 eb 0a 83 38 00 75 43 <89> 08 48 63 c1 48 39 c8 74 2e eb 48 83 38 00 75 32 48 29 c1 89 08
RSP: 0018:ffffb223c00dbb10 EFLAGS: 00010246
RAX: ffffffffc005b1d9 RBX: 0000000000000000 RCX: ffffffff8b200060
RDX: 000000000000000b RSI: 0000004b0000000b RDI: ffff96bdfcd33000
RBP: ffffb223c00dbb38 R08: ffffffffc005d040 R09: ffffffffc005c1f0
R10: ffff96bdfcd33c40 R11: ffff96bdfcd33b80 R12: 0000000000000018
R13: ffffffffc005c1f0 R14: ffffffffc005e708 R15: ffffffff8b2fbc74
FS: 00007f5f447beba8(0000) GS:ffff96bdff900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffc005b1d9 CR3: 000000003cedc002 CR4: 0000000000360ea0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
klp_init_object_loaded+0x10f/0x219
? preempt_latency_start+0x21/0x57
klp_enable_patch+0x662/0x809
? virt_to_head_page+0x3a/0x3c
? kfree+0x8c/0x126
patch_init+0x2ed/0x1000 [livepatch_test02]
? 0xffffffffc0060000
do_one_initcall+0x9f/0x1c5
? kmem_cache_alloc_trace+0xc4/0xd4
? do_init_module+0x27/0x210
do_init_module+0x5f/0x210
load_module+0x1c41/0x2290
? fsnotify_path+0x3b/0x42
? strstarts+0x2b/0x2b
? kernel_read+0x58/0x65
__do_sys_finit_module+0x9f/0xc3
? __do_sys_finit_module+0x9f/0xc3
__x64_sys_finit_module+0x1a/0x1c
do_syscall_64+0x52/0x61
entry_SYSCALL_64_after_hwframe+0x44/0xa9
The above panic occurs when loading two modules at the same time with
ftrace enabled, where at least one of the modules is a livepatch module:
CPU0 CPU1
klp_enable_patch()
klp_init_object_loaded()
module_disable_ro()
ftrace_module_enable()
ftrace_arch_code_modify_post_process()
set_all_modules_text_ro()
klp_write_object_relocations()
apply_relocate_add()
*patches read-only code* - BOOM
A similar race exists when toggling ftrace while loading a livepatch
module.
Fix it by ensuring that the livepatch and ftrace code patching
operations -- and their respective permissions changes -- are protected
by the text_mutex.
Link: http://lkml.kernel.org/r/ab43d56ab909469ac5d2520c5d944ad6d4abd476.1560474114.git.jpoimboe@redhat.com
Reported-by: Johannes Erdfelt <johannes@erdfelt.com>
Fixes: 444d13ff10
("modules: add ro_after_init support")
Acked-by: Jessica Yu <jeyu@kernel.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
parent
a4158345ec
commit
9f255b632b
2 changed files with 15 additions and 1 deletions
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@ -30,6 +30,7 @@
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#include <linux/elf.h>
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#include <linux/elf.h>
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#include <linux/moduleloader.h>
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#include <linux/moduleloader.h>
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#include <linux/completion.h>
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#include <linux/completion.h>
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#include <linux/memory.h>
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#include <asm/cacheflush.h>
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#include <asm/cacheflush.h>
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#include "core.h"
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#include "core.h"
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#include "patch.h"
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#include "patch.h"
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@ -730,16 +731,21 @@ static int klp_init_object_loaded(struct klp_patch *patch,
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struct klp_func *func;
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struct klp_func *func;
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int ret;
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int ret;
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mutex_lock(&text_mutex);
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module_disable_ro(patch->mod);
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module_disable_ro(patch->mod);
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ret = klp_write_object_relocations(patch->mod, obj);
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ret = klp_write_object_relocations(patch->mod, obj);
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if (ret) {
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if (ret) {
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module_enable_ro(patch->mod, true);
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module_enable_ro(patch->mod, true);
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mutex_unlock(&text_mutex);
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return ret;
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return ret;
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}
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}
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arch_klp_init_object_loaded(patch, obj);
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arch_klp_init_object_loaded(patch, obj);
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module_enable_ro(patch->mod, true);
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module_enable_ro(patch->mod, true);
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mutex_unlock(&text_mutex);
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klp_for_each_func(obj, func) {
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klp_for_each_func(obj, func) {
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ret = klp_find_object_symbol(obj->name, func->old_name,
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ret = klp_find_object_symbol(obj->name, func->old_name,
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func->old_sympos,
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func->old_sympos,
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@ -34,6 +34,7 @@
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#include <linux/hash.h>
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#include <linux/hash.h>
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#include <linux/rcupdate.h>
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#include <linux/rcupdate.h>
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#include <linux/kprobes.h>
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#include <linux/kprobes.h>
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#include <linux/memory.h>
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#include <trace/events/sched.h>
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#include <trace/events/sched.h>
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@ -2610,10 +2611,12 @@ static void ftrace_run_update_code(int command)
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{
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{
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int ret;
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int ret;
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mutex_lock(&text_mutex);
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ret = ftrace_arch_code_modify_prepare();
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ret = ftrace_arch_code_modify_prepare();
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FTRACE_WARN_ON(ret);
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FTRACE_WARN_ON(ret);
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if (ret)
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if (ret)
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return;
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goto out_unlock;
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/*
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/*
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* By default we use stop_machine() to modify the code.
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* By default we use stop_machine() to modify the code.
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@ -2625,6 +2628,9 @@ static void ftrace_run_update_code(int command)
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ret = ftrace_arch_code_modify_post_process();
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ret = ftrace_arch_code_modify_post_process();
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FTRACE_WARN_ON(ret);
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FTRACE_WARN_ON(ret);
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out_unlock:
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mutex_unlock(&text_mutex);
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}
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}
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static void ftrace_run_modify_code(struct ftrace_ops *ops, int command,
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static void ftrace_run_modify_code(struct ftrace_ops *ops, int command,
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@ -5775,6 +5781,7 @@ void ftrace_module_enable(struct module *mod)
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struct ftrace_page *pg;
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struct ftrace_page *pg;
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mutex_lock(&ftrace_lock);
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mutex_lock(&ftrace_lock);
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mutex_lock(&text_mutex);
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if (ftrace_disabled)
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if (ftrace_disabled)
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goto out_unlock;
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goto out_unlock;
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@ -5836,6 +5843,7 @@ void ftrace_module_enable(struct module *mod)
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ftrace_arch_code_modify_post_process();
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ftrace_arch_code_modify_post_process();
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out_unlock:
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out_unlock:
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mutex_unlock(&text_mutex);
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mutex_unlock(&ftrace_lock);
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mutex_unlock(&ftrace_lock);
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process_cached_mods(mod->name);
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process_cached_mods(mod->name);
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