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Commit 293a7cfe authored by Rusty Russell's avatar Rusty Russell Committed by Linus Torvalds
Browse files

module: fix reference to mod->percpu after freeing module. 



Rafael sees a sometimes crash at precpu_modfree from kernel/module.c; it
only occurred with another (since-reverted) patch, but that patch simply
changed timing to uncover this bug, it was otherwise unrelated.

The comment about the mod being freed is self-explanatory, but neither
Tejun nor I read it.  This bug was introduced in 259354de, after it
had previously been fixed in 6e2b7574.  How embarrassing.

Reported-by: default avatar"Rafael J. Wysocki" <rjw@sisk.pl>
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
Embarrassingly-Acked-by: default avatarTejun Heo <tj@kernel.org>
Cc: Masami Hiramatsu <mhiramat@redhat.com>
Tested-by: default avatar"Rafael J. Wysocki" <rjw@sisk.pl>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 67a3e12b

kernel/module.c

+4 −1
Original line number Diff line number Diff line
@@ -2014,6 +2014,7 @@ static noinline struct module *load_module(void __user *umod, 
	long err = 0;

	void *ptr = NULL; /* Stops spurious gcc warning */

	unsigned long symoffs, stroffs, *strmap;

	void __percpu *percpu;



	mm_segment_t old_fs;
@@ -2158,6 +2159,8 @@ static noinline struct module *load_module(void __user *umod, 
			goto free_mod;

		sechdrs[pcpuindex].sh_flags &= ~(unsigned long)SHF_ALLOC;

	}

	/* Keep this around for failure path. */

	percpu = mod_percpu(mod);



	/* Determine total sizes, and put offsets in sh_entsize.  For now

	   this is done generically; there doesn't appear to be any
@@ -2463,7 +2466,7 @@ static noinline struct module *load_module(void __user *umod, 
	module_free(mod, mod->module_core);

	/* mod will be freed with core. Don't access it beyond this line! */

 free_percpu:

	percpu_modfree(mod);

	free_percpu(percpu);

 free_mod:

	kfree(args);

	kfree(strmap);