This is a note to let you know that I've just added the patch titled
clk: Enforce that disjoints limits are invalid
to the 5.16-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
clk-enforce-that-disjoints-limits-are-invalid.patch
and it can be found in the queue-5.16 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit f17334e85186cb508c1af96ea9bcb029d32f6d0f
Author: Maxime Ripard <maxime@xxxxxxxxxx>
Date: Fri Feb 25 15:35:25 2022 +0100
clk: Enforce that disjoints limits are invalid
[ Upstream commit 10c46f2ea914202482d19cf80dcc9c321c9ff59b ]
If we were to have two users of the same clock, doing something like:
clk_set_rate_range(user1, 1000, 2000);
clk_set_rate_range(user2, 3000, 4000);
The second call would fail with -EINVAL, preventing from getting in a
situation where we end up with impossible limits.
However, this is never explicitly checked against and enforced, and
works by relying on an undocumented behaviour of clk_set_rate().
Indeed, on the first clk_set_rate_range will make sure the current clock
rate is within the new range, so it will be between 1000 and 2000Hz. On
the second clk_set_rate_range(), it will consider (rightfully), that our
current clock is outside of the 3000-4000Hz range, and will call
clk_core_set_rate_nolock() to set it to 3000Hz.
clk_core_set_rate_nolock() will then call clk_calc_new_rates() that will
eventually check that our rate 3000Hz rate is outside the min 3000Hz max
2000Hz range, will bail out, the error will propagate and we'll
eventually return -EINVAL.
This solely relies on the fact that clk_calc_new_rates(), and in
particular clk_core_determine_round_nolock(), won't modify the new rate
allowing the error to be reported. That assumption won't be true for all
drivers, and most importantly we'll break that assumption in a later
patch.
It can also be argued that we shouldn't even reach the point where we're
calling clk_core_set_rate_nolock().
Let's make an explicit check for disjoints range before we're doing
anything.
Signed-off-by: Maxime Ripard <maxime@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20220225143534.405820-4-maxime@xxxxxxxxxx
Signed-off-by: Stephen Boyd <sboyd@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 2c5db2df9d42..aaf2793ef638 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -631,6 +631,24 @@ static void clk_core_get_boundaries(struct clk_core *core,
*max_rate = min(*max_rate, clk_user->max_rate);
}
+static bool clk_core_check_boundaries(struct clk_core *core,
+ unsigned long min_rate,
+ unsigned long max_rate)
+{
+ struct clk *user;
+
+ lockdep_assert_held(&prepare_lock);
+
+ if (min_rate > core->max_rate || max_rate < core->min_rate)
+ return false;
+
+ hlist_for_each_entry(user, &core->clks, clks_node)
+ if (min_rate > user->max_rate || max_rate < user->min_rate)
+ return false;
+
+ return true;
+}
+
void clk_hw_set_rate_range(struct clk_hw *hw, unsigned long min_rate,
unsigned long max_rate)
{
@@ -2347,6 +2365,11 @@ int clk_set_rate_range(struct clk *clk, unsigned long min, unsigned long max)
clk->min_rate = min;
clk->max_rate = max;
+ if (!clk_core_check_boundaries(clk->core, min, max)) {
+ ret = -EINVAL;
+ goto out;
+ }
+
rate = clk_core_get_rate_nolock(clk->core);
if (rate < min || rate > max) {
/*
@@ -2375,6 +2398,7 @@ int clk_set_rate_range(struct clk *clk, unsigned long min, unsigned long max)
}
}
+out:
if (clk->exclusive_count)
clk_core_rate_protect(clk->core);
