From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932987AbXCPLfo (ORCPT ); Fri, 16 Mar 2007 07:35:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S933029AbXCPLfo (ORCPT ); Fri, 16 Mar 2007 07:35:44 -0400 Received: from mailhub.sw.ru ([195.214.233.200]:18650 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932987AbXCPLfn (ORCPT ); Fri, 16 Mar 2007 07:35:43 -0400 Date: Fri, 16 Mar 2007 14:42:45 +0300 From: Alexey Dobriyan To: akpm@osdl.org Cc: linux-kernel@vger.kernel.org, devel@openvz.org, pmarques@grupopie.com Subject: [PATCH RESEND 1/2] Race between cat /proc/kallsyms and rmmod Message-ID: <20070316114245.GA6817@localhost.sw.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org CONFIG_MODULES=n case fixed, We're still discussing if making module_mutex global is OK, though. ----------------------------------------------------- [PATCH 1/2] Race between cat /proc/kallsyms and rmmod Iterating code of /proc/kallsyms calls module_get_kallsym() which grabs and drops module_mutex internally and returns "struct module *", module is removed, aforementioned "struct module *" is used in non-trivial way. So, grab module_mutex for entire operation like /proc/modules does. Steps to reproduce: while true; do modprobe xfs; rmmod xfs; done vs while true; do cat /proc/kallsyms >/dev/null; done [where xfs could be any module, I haven't tried] BUG: unable to handle kernel paging request at virtual address e19f808c printing eip: c01dc361 *pde = 1ff5f067 *pte = 00000000 Oops: 0000 [#1] PREEMPT Modules linked in: CPU: 0 EIP: 0060:[] Not tainted VLI EFLAGS: 00010297 (2.6.21-rc3-8b9909ded6922c33c221b105b26917780cfa497d #2) EIP is at vsnprintf+0x2af/0x48c eax: e19f808c ebx: ffffffff ecx: e19f808c edx: fffffffe esi: dbe7aa84 edi: dbe2bf3c ebp: ffffffff esp: dbe2bec4 ds: 007b es: 007b fs: 00d8 gs: 0033 ss: 0068 Process cat (pid: 7242, ti=dbe2b000 task=df5790b0 task.ti=dbe2b000) Stack: e19d6fde 00000000 00000010 00000008 ffffffff 00000001 00000598 dbe7aa68 0002f362 00000010 dbe7b000 00000000 ffffffff c034bbe0 dbe7aa68 dfd31880 dfa31e80 00001000 c01586b0 dbe2bf2c dbe2bf2c dfd31880 dfd31880 c01289f6 Call Trace: [] seq_printf+0x2e/0x4b [] s_show+0x4b/0x7f [] seq_read+0x196/0x278 [] seq_read+0x0/0x278 [] vfs_read+0x72/0x93 [] sys_read+0x41/0x67 [] sysenter_past_esp+0x5f/0x85 ======================= Code: 74 24 28 73 03 c6 06 20 46 4d 85 ed 7f f1 e9 b9 00 00 00 8b 0f 81 f9 ff 0f 00 00 b8 ea 45 36 c0 0f 46 c8 8b 54 24 30 89 c8 eb 06 <80> 38 00 74 07 40 4a 83 fa ff 75 f4 29 c8 89 c3 89 e8 f6 44 24 EIP: [] vsnprintf+0x2af/0x48c SS:ESP 0068:dbe2bec4 Signed-off-by: Alexey Dobriyan --- include/linux/module.h | 14 ++++++++++++++ kernel/kallsyms.c | 2 ++ kernel/module.c | 15 +++++++++++---- 3 files changed, 27 insertions(+), 4 deletions(-) --- a/include/linux/module.h +++ b/include/linux/module.h @@ -16,10 +16,24 @@ #include #include #include #include +#include #include #include +extern struct mutex module_mutex; +#ifdef CONFIG_MODULES +void module_mutex_lock(void); +void module_mutex_unlock(void); +#else +static inline void module_mutex_lock(void) +{ +} +static inline void module_mutex_unlock(void) +{ +} +#endif + /* Not Yet Implemented */ #define MODULE_SUPPORTED_DEVICE(name) --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -369,6 +369,7 @@ static void *s_next(struct seq_file *m, static void *s_start(struct seq_file *m, loff_t *pos) { + module_mutex_lock(); if (!update_iter(m->private, *pos)) return NULL; return m->private; @@ -376,6 +377,7 @@ static void *s_start(struct seq_file *m, static void s_stop(struct seq_file *m, void *p) { + module_mutex_unlock(); } static int s_show(struct seq_file *m, void *p) --- a/kernel/module.c +++ b/kernel/module.c @@ -62,9 +62,19 @@ #define INIT_OFFSET_MASK (1UL << (BITS_P static DEFINE_SPINLOCK(modlist_lock); /* List of modules, protected by module_mutex AND modlist_lock */ -static DEFINE_MUTEX(module_mutex); +DEFINE_MUTEX(module_mutex); static LIST_HEAD(modules); +void module_mutex_lock(void) +{ + mutex_lock(&module_mutex); +} + +void module_mutex_unlock(void) +{ + mutex_unlock(&module_mutex); +} + static BLOCKING_NOTIFIER_HEAD(module_notify_list); int register_module_notifier(struct notifier_block * nb) @@ -2124,19 +2134,16 @@ struct module *module_get_kallsym(unsign { struct module *mod; - mutex_lock(&module_mutex); list_for_each_entry(mod, &modules, list) { if (symnum < mod->num_symtab) { *value = mod->symtab[symnum].st_value; *type = mod->symtab[symnum].st_info; strlcpy(name, mod->strtab + mod->symtab[symnum].st_name, namelen); - mutex_unlock(&module_mutex); return mod; } symnum -= mod->num_symtab; } - mutex_unlock(&module_mutex); return NULL; }