Messages in this thread | | | From | Nick Desaulniers <> | Date | Tue, 27 Apr 2021 12:19:40 -0700 | Subject | Re: [PATCH] bus: fsl-mc: fix improper free of mc_dev |
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On Tue, Apr 27, 2021 at 11:36 AM <trix@redhat.com> wrote: > > From: Tom Rix <trix@redhat.com> > > Clang static analysis reports this error > > fsl-mc-bus.c:891:2: warning: Attempt to free released memory > kfree(mc_dev); > ^~~~~~~~~~~~~ > > In this block of code > > if (strcmp(obj_desc->type, "dprc") == 0) { > .. > mc_bus = kzalloc(..) > mc_dev = &mc_bus->mc_dev;
Thanks for the patch.
Aren't the allocations for mc_bus and mc_dev mutually exclusive based on that conditional? If so...
> > mc_dev is not alloc-ed, so it should not be freed. > Old handler triggers a false positive from checkpatch, so add a > comment and change logic a bit. > > Fixes: a042fbed0290 ("staging: fsl-mc: simplify couple of deallocations") > Signed-off-by: Tom Rix <trix@redhat.com> > --- > drivers/bus/fsl-mc/fsl-mc-bus.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/drivers/bus/fsl-mc/fsl-mc-bus.c b/drivers/bus/fsl-mc/fsl-mc-bus.c > index 380ad1fdb745..fb3e1d8a7f63 100644 > --- a/drivers/bus/fsl-mc/fsl-mc-bus.c > +++ b/drivers/bus/fsl-mc/fsl-mc-bus.c > @@ -887,8 +887,10 @@ int fsl_mc_device_add(struct fsl_mc_obj_desc *obj_desc, > > error_cleanup_dev: > kfree(mc_dev->regions); > + /* mc_dev is only allocated when it is not part of mc_bus */ > + if (!mc_bus) > + kfree(mc_dev); > kfree(mc_bus); > - kfree(mc_dev);
The error handling here seems quite wrong (regardless of your patch). mc_dev->regions is allocated by fsl_mc_device_get_mmio_regions() IIUC. Wouldn't the first `goto error_cleanup_dev;` taken end up passing an uninitialized pointer to kfree()?
what if `strcmp(obj_desc->type, "dprc") == 0` is false? We allocate `mc_dev`, but then call kfree on `mc_bus`?
I think it would be safer to locally save the result of `strcmp(obj_desc->type, "dprc") == 0`, then check that throughout this function, including the error handling at the end, or use multiple labels to unwind the allocations correctly.
> > return error; > }
> --
-- Thanks, ~Nick Desaulniers
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