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net/sched: taprio: extend minimum interval restriction to entire cycle too

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It is possible for syzbot to side-step the restriction imposed by the
blamed commit in the Fixes: tag, because the taprio UAPI permits a
cycle-time different from (and potentially shorter than) the sum of
entry intervals.

We need one more restriction, which is that the cycle time itself must
be larger than N * ETH_ZLEN bit times, where N is the number of schedule
entries. This restriction needs to apply regardless of whether the cycle
time came from the user or was the implicit, auto-calculated value, so
we move the existing "cycle == 0" check outside the "if "(!new->cycle_time)"
branch. This way covers both conditions and scenarios.

Add a selftest which illustrates the issue triggered by syzbot.

Fixes: b5b73b26b3 ("taprio: Fix allowing too small intervals")
Reported-by: syzbot+a7d2b1d5d1af83035567@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/0000000000007d66bc06196e7c66@google.com/
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://lore.kernel.org/r/20240527153955.553333-2-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Vladimir Oltean
2024-05-27 18:39:55 +03:00
committed by Jakub Kicinski
parent e634134180
commit fb66df20a7
2 changed files with 27 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
net/sched/sch_taprio.c
View File

@ -1151,11 +1151,6 @@ static int parse_taprio_schedule(struct taprio_sched *q, struct nlattr **tb,
list_for_each_entry(entry, &new->entries, list)
cycle = ktime_add_ns(cycle, entry->interval);
if (!cycle) {
NL_SET_ERR_MSG(extack, "'cycle_time' can never be 0");
return -EINVAL;
}
if (cycle < 0 || cycle > INT_MAX) {
NL_SET_ERR_MSG(extack, "'cycle_time' is too big");
return -EINVAL;
@ -1164,6 +1159,11 @@ static int parse_taprio_schedule(struct taprio_sched *q, struct nlattr **tb,
new->cycle_time = cycle;
}
if (new->cycle_time < new->num_entries * length_to_duration(q, ETH_ZLEN)) {
NL_SET_ERR_MSG(extack, "'cycle_time' is too small");
return -EINVAL;
}
taprio_calculate_gate_durations(q, new);
return 0;