media: atomisp: revert "don't pass a pointer to a local variable"

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[ Upstream commit a3b36a8ce3 ]

The gcc is warning about returning a pointer to a local variable
is a false positive.

The type of handle is "struct ia_css_rmgr_vbuf_handle **" and
"h.vptr" is left to NULL, so the "if ((*handle)->vptr == 0x0)"
check always succeeds when the "*handle = &h;" statement which
gcc warns about executes. Leading to this statement being executed:

	rmgr_pop_handle(pool, handle);

If that succeeds,  then *handle has been set to point to one of
the pre-allocated array of handles, so it no longer points to h.

If that fails the following statement will be executed:

	/* Note that handle will change to an internally maintained one */
	ia_css_rmgr_refcount_retain_vbuf(handle);

Which allocated a new handle from the array of pre-allocated handles
and then makes *handle point to this. So the address of h is actually
never returned.

The fix for the false-postive compiler warning actually breaks the code,
the new:

	**handle = h;

is part of a "if (pool->copy_on_write) { ... }" which means that the
handle where *handle points to should be treated read-only, IOW
**handle must never be set, instead *handle must be set to point to
a new handle (with a copy of the contents of the old handle).

The old code correctly did this and the new fixed code gets this wrong.

Note there is another patch in this series, which fixes the warning
in another way.

Link: https://lore.kernel.org/linux-media/20220612160556.108264-2-hdegoede@redhat.com
Fixes: fa1451374e ("media: atomisp: don't pass a pointer to a local variable")
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

...

This commit is contained in:

Hans de Goede 2022-06-12 17:05:54 +01:00 • committed by Greg Kroah-Hartman

parent 8516d329dc

commit 2090efd157

1 changed files with 2 additions and 2 deletions

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drivers/staging/media/atomisp/pci/runtime/rmgr/src/rmgr_vbuf.c

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