Commit 5e376613899076396d0c97de67ad072587267370

Authored by Trent Piepho
Committed by Linus Torvalds
1 parent 0159677857

[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>

Showing 3 changed files with 8 additions and 7 deletions Side-by-side Diff

include/linux/kernel.h
... ... @@ -124,6 +124,7 @@
124 124 extern char *get_options(const char *str, int nints, int *ints);
125 125 extern unsigned long long memparse(char *ptr, char **retptr);
126 126  
  127 +extern int core_kernel_text(unsigned long addr);
127 128 extern int __kernel_text_address(unsigned long addr);
128 129 extern int kernel_text_address(unsigned long addr);
129 130 extern int session_of_pgrp(int pgrp);
... ... @@ -40,7 +40,7 @@
40 40 return e;
41 41 }
42 42  
43   -static int core_kernel_text(unsigned long addr)
  43 +int core_kernel_text(unsigned long addr)
44 44 {
45 45 if (addr >= (unsigned long)_stext &&
46 46 addr <= (unsigned long)_etext)
... ... @@ -705,14 +705,14 @@
705 705  
706 706 void symbol_put_addr(void *addr)
707 707 {
708   - unsigned long flags;
  708 + struct module *modaddr;
709 709  
710   - spin_lock_irqsave(&modlist_lock, flags);
711   - if (!kernel_text_address((unsigned long)addr))
712   - BUG();
  710 + if (core_kernel_text((unsigned long)addr))
  711 + return;
713 712  
714   - module_put(module_text_address((unsigned long)addr));
715   - spin_unlock_irqrestore(&modlist_lock, flags);
  713 + if (!(modaddr = module_text_address((unsigned long)addr)))
  714 + BUG();
  715 + module_put(modaddr);
716 716 }
717 717 EXPORT_SYMBOL_GPL(symbol_put_addr);
718 718