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firmware: arm_scmi: Fix bound iterators returning too many items

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When using a bound-iterator with an upper bound, commands are sent, and
responses are received, until the upper bound is reached.  However, it
is up to the SCMI provider implementation to decide how many rates are
returned in response to a single CLOCK_DESCRIBE_RATES command.  If the
last response contains rates beyond the specified upper bound, they are
still passed up for further processing.  This may lead to buffer
overflows in unprepared callsites.

While the imprecise bound handling may have been intentional (it was
mentioned in the commit message introducing the code), it is still
confusing for users, and may cause hard to debug crashes.  Fix this by
strictly enforcing the upper bound.

Note that this may cause an increase in the number of
CLOCK_DESCRIBE_RATES commands issued, as retrieving the last rate may no
longer be done inadvertentently, but require its own command.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Tested-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://patch.msgid.link/20260508153300.2224715-12-cristian.marussi@arm.com
Signed-off-by: Sudeep Holla <sudeep.holla@kernel.org>
This commit is contained in:
Geert Uytterhoeven 2026-05-08 16:32:56 +01:00 committed by Sudeep Holla
parent 4848d07ea9
commit ae4a088f13
1 changed files with 7 additions and 2 deletions
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9
drivers/firmware/arm_scmi/driver.c
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@ -1820,6 +1820,7 @@ static int __scmi_iterator_run(void *iter, unsigned int *start, unsigned int *en
const struct scmi_protocol_handle *ph;
struct scmi_iterator_state *st;
struct scmi_iterator *i;
unsigned int n;
if (!iter)
return -EINVAL;
@ -1852,13 +1853,17 @@ static int __scmi_iterator_run(void *iter, unsigned int *start, unsigned int *en
return -EINVAL;
}
for (st->loop_idx = 0; st->loop_idx < st->num_returned; st->loop_idx++) {
if (end)
n = min(st->num_returned, *end - st->desc_index + 1);
else
n = st->num_returned;
for (st->loop_idx = 0; st->loop_idx < n; st->loop_idx++) {
ret = iops->process_response(ph, i->resp, st, i->priv);
if (ret)
return ret;
}
st->desc_index += st->num_returned;
st->desc_index += n;
ph->xops->reset_rx_to_maxsz(ph, i->t);
/*
* check for both returned and remaining to avoid infinite