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Commit 5336377d authored Oct 05, 2010 by Linus Torvalds

modules: Fix module_bug_list list corruption race



With all the recent module loading cleanups, we've minimized the code
that sits under module_mutex, fixing various deadlocks and making it
possible to do most of the module loading in parallel.

However, that whole conversion totally missed the rather obscure code
that adds a new module to the list for BUG() handling.  That code was
doubly obscure because (a) the code itself lives in lib/bugs.c (for
dubious reasons) and (b) it gets called from the architecture-specific
"module_finalize()" rather than from generic code.

Calling it from arch-specific code makes no sense what-so-ever to begin
with, and is now actively wrong since that code isn't protected by the
module loading lock any more.

So this commit moves the "module_bug_{finalize,cleanup}()" calls away
from the arch-specific code, and into the generic code - and in the
process protects it with the module_mutex so that the list operations
are now safe.

Future fixups:
 - move the module list handling code into kernel/module.c where it
   belongs.
 - get rid of 'module_bug_list' and just use the regular list of modules
   (called 'modules' - imagine that) that we already create and maintain
   for other reasons.

Reported-and-tested-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Adrian Bunk <bunk@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 2f6b3aa7

arch/avr32/kernel/module.c

+1 −2

Original line number	Diff line number	Diff line
		@@ -314,10 +314,9 @@ int module_finalize(const Elf_Ehdr hdr, const Elf_Shdr sechdrs,
		vfree(module->arch.syminfo);
		module->arch.syminfo = NULL;

		return module_bug_finalize(hdr, sechdrs, module);
		return 0;
		}

		void module_arch_cleanup(struct module *module)
		{
		module_bug_cleanup(module);
		}

arch/h8300/kernel/module.c

+1 −2

Original line number	Diff line number	Diff line
		@@ -112,10 +112,9 @@ int module_finalize(const Elf_Ehdr *hdr,
		const Elf_Shdr *sechdrs,
		struct module *me)
		{
		return module_bug_finalize(hdr, sechdrs, me);
		return 0;
		}

		void module_arch_cleanup(struct module *mod)
		{
		module_bug_cleanup(mod);
		}

arch/mn10300/kernel/module.c

+1 −2

Original line number	Diff line number	Diff line
		@@ -206,7 +206,7 @@ int module_finalize(const Elf_Ehdr *hdr,
		const Elf_Shdr *sechdrs,
		struct module *me)
		{
		return module_bug_finalize(hdr, sechdrs, me);
		return 0;
		}

		/*
		@@ -214,5 +214,4 @@ int module_finalize(const Elf_Ehdr *hdr,
		*/
		void module_arch_cleanup(struct module *mod)
		{
		module_bug_cleanup(mod);
		}

arch/parisc/kernel/module.c

+1 −2

Original line number	Diff line number	Diff line
		@@ -941,11 +941,10 @@ int module_finalize(const Elf_Ehdr *hdr,
		nsyms = newptr - (Elf_Sym *)symhdr->sh_addr;
		DEBUGP("NEW num_symtab %lu\n", nsyms);
		symhdr->sh_size = nsyms * sizeof(Elf_Sym);
		return module_bug_finalize(hdr, sechdrs, me);
		return 0;
		}

		void module_arch_cleanup(struct module *mod)
		{
		deregister_unwind_table(mod);
		module_bug_cleanup(mod);
		}

arch/powerpc/kernel/module.c

+0 −5

Original line number	Diff line number	Diff line
		@@ -65,10 +65,6 @@ int module_finalize(const Elf_Ehdr *hdr,
		const Elf_Shdr *sect;
		int err;

		err = module_bug_finalize(hdr, sechdrs, me);
		if (err)
		return err;

		/* Apply feature fixups */
		sect = find_section(hdr, sechdrs, "__ftr_fixup");
		if (sect != NULL)
		@@ -101,5 +97,4 @@ int module_finalize(const Elf_Ehdr *hdr,

		void module_arch_cleanup(struct module *mod)
		{
		module_bug_cleanup(mod);
		}