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SubjectRe: [PATCH 1/3] binfmt_elf: Respect error return from `regset->active'
Hi Alexander,

On Tue, May 15, 2018 at 11:32:45PM +0100, Maciej W. Rozycki wrote:
> The regset API documented in <linux/regset.h> defines -ENODEV as the
> result of the `->active' handler to be used where the feature requested
> is not available on the hardware found. However code handling core file
> note generation in `fill_thread_core_info' interpretes any non-zero
> result from the `->active' handler as the regset requested being active.
> Consequently processing continues (and hopefully gracefully fails later
> on) rather than being abandoned right away for the regset requested.
>
> Fix the problem then by making the code proceed only if a positive
> result is returned from the `->active' handler.
>
> Cc: stable@vger.kernel.org # 2.6.25+
> Fixes: 4206d3aa1978 ("elf core dump: notes user_regset")
> Signed-off-by: Maciej W. Rozycki <macro@mips.com>

<snip>

> --- linux-jhogan-test.orig/fs/binfmt_elf.c 2018-03-21 17:14:55.000000000 +0000
> +++ linux-jhogan-test/fs/binfmt_elf.c 2018-05-09 23:25:50.742255000 +0100
> @@ -1739,7 +1739,7 @@ static int fill_thread_core_info(struct
> const struct user_regset *regset = &view->regsets[i];
> do_thread_regset_writeback(t->task, regset);
> if (regset->core_note_type && regset->get &&
> - (!regset->active || regset->active(t->task, regset))) {
> + (!regset->active || regset->active(t->task, regset) > 0)) {
> int ret;
> size_t size = regset_size(t->task, regset);
> void *data = kmalloc(size, GFP_KERNEL);
>

This looks obviously right to me, although I don't think it affects
anything until commit 25847fb195ae ("powerpc/ptrace: Enable support for
NT_PPC_CGPR") in v4.8-rc1 & even then not in a harmful way so I'd drop
the stable tag.

You show up as maintainer for fs/binfmt_elf.c though, so before I go
applying this to mips-next does it look good to you?

Thanks,
Paul

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