Messages in this thread Patch in this message |  | | From | Mashiro Chen <> | | Subject | [PATCH] sched/psi: initialize *flags in psi_memstall_enter when PSI is disabled | | Date | Sun, 5 Apr 2026 13:50:44 +0800 |
| |
When PSI is disabled, psi_memstall_enter() returns early without writing to *flags, leaving the caller's local variable uninitialized. psi_memstall_leave() also returns early when PSI is disabled and does not read *flags, so the uninitialized value is never used functionally.
However, KMSAN tracks the shadow and origin metadata per physical address. When a kernel stack page is subsequently reused, a new object at the same address inherits the stale KMSAN shadow from the old uninitialized pflags, causing spurious uninit-value reports in unrelated code paths such as __flush_smp_call_function_queue().
Initialize *flags to 0 in the psi_disabled early-return path to prevent the stale shadow from escaping the callers' stack frames.
Fixes: eb414681d5a0 ("psi: pressure stall information for CPU, memory, and IO") Reported-by: syzbot+4b1bd55fba6260160779@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=4b1bd55fba6260160779 Link: https://lore.kernel.org/all/6991885b.050a0220.340abe.02ef.GAE@google.com/ Signed-off-by: Mashiro Chen <mashiro.chen@mailbox.org> --- kernel/sched/psi.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c index d9c9d9480a45b..32d3a180fc03b 100644 --- a/kernel/sched/psi.c +++ b/kernel/sched/psi.c @@ -1058,8 +1058,10 @@ void psi_memstall_enter(unsigned long *flags) struct rq_flags rf; struct rq *rq; - if (static_branch_likely(&psi_disabled)) + if (static_branch_likely(&psi_disabled)) { + *flags = 0; return; + } *flags = current->in_memstall; if (*flags) -- 2.53.0
|  |