[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 <xyzzy@speakeasy.org>
Cc: Zwane Mwaikambo <zwane@fsmlabs.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Johannes Stezenbach <js@linuxtv.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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 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 @@
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 @@
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))
+ if (core_kernel_text((unsigned long)addr))
+ return;
+
+ if (!(modaddr = module_text_address((unsigned long)addr)))
BUG();
-
- module_put(module_text_address((unsigned long)addr));
- spin_unlock_irqrestore(&modlist_lock, flags);
+ module_put(modaddr);
}
EXPORT_SYMBOL_GPL(symbol_put_addr);