[PATCH AUTOSEL 4.4 01/20] binfmt_elf: Respect error return from `regset->active'

[Sasha Levin]

From: "Maciej W. Rozycki" <macro@xxxxxxxx>

[ Upstream commit 2f819db565e82e5f73cd42b39925098986693378 ]

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.

Signed-off-by: Maciej W. Rozycki <macro@xxxxxxxx>
Signed-off-by: Paul Burton <paul.burton@xxxxxxxx>
Fixes: 4206d3aa1978 ("elf core dump: notes user_regset")
Patchwork: https://patchwork.linux-mips.org/patch/19332/
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: James Hogan <jhogan@xxxxxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
Cc: linux-mips@xxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
---
 fs/binfmt_elf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index f44e93d2650d..62bc72001fce 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1707,7 +1707,7 @@ static int fill_thread_core_info(struct elf_thread_core_info *t,
 		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->n * regset->size;
 			void *data = kmalloc(size, GFP_KERNEL);
-- 
2.17.1