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

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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 259354deaa, after it
had previously been fixed in 6e2b75740b.  How embarrassing.

Reported-by: "Rafael J. Wysocki" <rjw@sisk.pl>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Embarrassingly-Acked-by: Tejun Heo <tj@kernel.org>
Cc: Masami Hiramatsu <mhiramat@redhat.com>
Tested-by: "Rafael J. Wysocki" <rjw@sisk.pl>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Rusty Russell 2010-05-31 19:53:50 +09:30 committed by Linus Torvalds
parent 67a3e12b05
commit 293a7cfeed
1 changed files with 4 additions and 1 deletions
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5
kernel/module.c
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@ -2014,6 +2014,7 @@ static noinline struct module *load_module(void __user *umod,
long err = 0; long err = 0;
void *ptr = NULL; /* Stops spurious gcc warning */ void *ptr = NULL; /* Stops spurious gcc warning */
unsigned long symoffs, stroffs, *strmap; unsigned long symoffs, stroffs, *strmap;
void __percpu *percpu;
mm_segment_t old_fs; mm_segment_t old_fs;
@ -2158,6 +2159,8 @@ static noinline struct module *load_module(void __user *umod,
goto free_mod; goto free_mod;
sechdrs[pcpuindex].sh_flags &= ~(unsigned long)SHF_ALLOC; 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 /* Determine total sizes, and put offsets in sh_entsize. For now
this is done generically; there doesn't appear to be any 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); module_free(mod, mod->module_core);
/* mod will be freed with core. Don't access it beyond this line! */ /* mod will be freed with core. Don't access it beyond this line! */
free_percpu: free_percpu:
percpu_modfree(mod); free_percpu(percpu);
free_mod: free_mod:
kfree(args); kfree(args);
kfree(strmap); kfree(strmap);