Commit 5e376613 authored by Trent Piepho's avatar Trent Piepho Committed by Linus Torvalds

[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: default avatarTrent Piepho <xyzzy@speakeasy.org>
Cc: Zwane Mwaikambo <zwane@fsmlabs.com>
Acked-by: default avatarRusty Russell <rusty@rustcorp.com.au>
Cc: Johannes Stezenbach <js@linuxtv.org>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 01596778
......@@ -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);
......
......@@ -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)
......
......@@ -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);
......
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