The patch titled
symbol_put_addr() locks kernel
has been added to the -mm tree. Its filename is
symbol_put_addr-locks-kernel.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
From: Trent Piepho <xyzzy@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxx>
Cc: Zwane Mwaikambo <zwane@xxxxxxxxxxx>
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
include/linux/kernel.h | 1 +
kernel/extable.c | 2 +-
kernel/module.c | 12 ++++++------
3 files changed, 8 insertions(+), 7 deletions(-)
diff -puN include/linux/kernel.h~symbol_put_addr-locks-kernel include/linux/kernel.h
--- 25/include/linux/kernel.h~symbol_put_addr-locks-kernel Mon May 8 12:31:30 2006
+++ 25-akpm/include/linux/kernel.h Mon May 8 12:31:30 2006
@@ -128,6 +128,7 @@ extern int get_option(char **str, int *p
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 -puN kernel/extable.c~symbol_put_addr-locks-kernel kernel/extable.c
--- 25/kernel/extable.c~symbol_put_addr-locks-kernel Mon May 8 12:31:30 2006
+++ 25-akpm/kernel/extable.c Mon May 8 12:31:30 2006
@@ -40,7 +40,7 @@ const struct exception_table_entry *sear
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 -puN kernel/module.c~symbol_put_addr-locks-kernel kernel/module.c
--- 25/kernel/module.c~symbol_put_addr-locks-kernel Mon May 8 12:31:30 2006
+++ 25-akpm/kernel/module.c Mon May 8 12:31:30 2006
@@ -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);
_
Patches currently in -mm which might be from xyzzy@xxxxxxxxxxxxx are
git-dvb.patch
symbol_put_addr-locks-kernel.patch
-
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