From 5e376613899076396d0c97de67ad072587267370 Mon Sep 17 00:00:00 2001 From: Trent Piepho Date: Mon, 15 May 2006 09:44:06 -0700 Subject: [PATCH] [PATCH] symbol_put_addr() locks kernel Even since a previous patch: Fix race between CONFIG_DEBUG_SLABALLOC and modules Sun, 27 Jun 2004 17:55:19 +0000 (17:55 +0000) http://www.kernel.org/git/?p=linux/kernel/git/torvalds/old-2.6-bkcvs.git;a=commit;h=92b3db26d31cf21b70e3c1eadc56c179506d8fbe The function symbol_put_addr() will deadlock the kernel. symbol_put_addr() would acquire modlist_lock, then while holding the lock call two functions kernel_text_address() and module_text_address() which also try to acquire the same lock. This deadlocks the kernel of course. This patch changes symbol_put_addr() to not acquire the modlist_lock, it doesn't need it since it never looks at the module list directly. Also, it now uses core_kernel_text() instead of kernel_text_address(). The latter has an additional check for addr inside a module, but we don't need to do that since we call module_text_address() (the same function kernel_text_address uses) ourselves. Signed-off-by: Trent Piepho Cc: Zwane Mwaikambo Acked-by: Rusty Russell Cc: Johannes Stezenbach Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/kernel.h | 1 + kernel/extable.c | 2 +- kernel/module.c | 12 ++++++------ 3 files changed, 8 insertions(+), 7 deletions(-) diff --git a/include/linux/kernel.h b/include/linux/kernel.h index e1bd084..f4fc576 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -124,6 +124,7 @@ extern int get_option(char **str, int *pint); extern char *get_options(const char *str, int nints, int *ints); extern unsigned long long memparse(char *ptr, char **retptr); +extern int core_kernel_text(unsigned long addr); extern int __kernel_text_address(unsigned long addr); extern int kernel_text_address(unsigned long addr); extern int session_of_pgrp(int pgrp); diff --git a/kernel/extable.c b/kernel/extable.c index 7501b53..7fe2628 100644 --- a/kernel/extable.c +++ b/kernel/extable.c @@ -40,7 +40,7 @@ const struct exception_table_entry *search_exception_tables(unsigned long addr) return e; } -static int core_kernel_text(unsigned long addr) +int core_kernel_text(unsigned long addr) { if (addr >= (unsigned long)_stext && addr <= (unsigned long)_etext) diff --git a/kernel/module.c b/kernel/module.c index d24deb0..bbe0486 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -705,14 +705,14 @@ EXPORT_SYMBOL(__symbol_put); void symbol_put_addr(void *addr) { - unsigned long flags; + struct module *modaddr; - spin_lock_irqsave(&modlist_lock, flags); - if (!kernel_text_address((unsigned long)addr)) - BUG(); + if (core_kernel_text((unsigned long)addr)) + return; - module_put(module_text_address((unsigned long)addr)); - spin_unlock_irqrestore(&modlist_lock, flags); + if (!(modaddr = module_text_address((unsigned long)addr))) + BUG(); + module_put(modaddr); } EXPORT_SYMBOL_GPL(symbol_put_addr); -- 2.7.4