diff options
author | Maxime Ripard <maxime@cerno.tech> | 2022-02-25 17:35:25 +0300 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-04-13 21:59:12 +0300 |
commit | b07387c476a350b74f1bcb8efc9b4c84e47e7a91 (patch) | |
tree | e05e93ec330aaedba76cece4a23b8d860d355624 /drivers/clk | |
parent | 15bfec9d8030c7e0122aa4a955c0cdb57d2256b9 (diff) | |
download | linux-b07387c476a350b74f1bcb8efc9b4c84e47e7a91.tar.xz |
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@cerno.tech>
Link: https://lore.kernel.org/r/20220225143534.405820-4-maxime@cerno.tech
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'drivers/clk')
-rw-r--r-- | drivers/clk/clk.c | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index 5cef73a85901..d6dc58bd07b3 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); |