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liveupdate: synchronize lazy initialization of FLB private state

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The luo_flb_get_private() function, which is responsible for lazily
initializing the private state of FLB objects, can be called concurrently
from multiple threads.  This creates a data race on the 'initialized' flag
and can lead to multiple executions of mutex_init() and INIT_LIST_HEAD()
on the same memory.

Introduce a static spinlock (luo_flb_init_lock) local to the function to
synchronize the initialization path.  Use smp_load_acquire() and
smp_store_release() for memory ordering between the fast path and the slow
path.

Link: https://lore.kernel.org/20260327033335.696621-3-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Cc: David Matlack <dmatlack@google.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Samiullah Khawaja <skhawaja@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Pasha Tatashin
2026-03-27 03:33:26 +00:00
committed by Andrew Morton
parent 277f4e5e39
commit 38fb71ace2
1 changed files with 6 additions and 1 deletions
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7
kernel/liveupdate/luo_flb.c
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@@ -89,13 +89,18 @@ struct luo_flb_link {
static struct luo_flb_private *luo_flb_get_private(struct liveupdate_flb *flb)
{
struct luo_flb_private *private = &ACCESS_PRIVATE(flb, private);
static DEFINE_SPINLOCK(luo_flb_init_lock);
if (smp_load_acquire(&private->initialized))
return private;
guard(spinlock)(&luo_flb_init_lock);
if (!private->initialized) {
mutex_init(&private->incoming.lock);
mutex_init(&private->outgoing.lock);
INIT_LIST_HEAD(&private->list);
private->users = 0;
private->initialized = true;
smp_store_release(&private->initialized, true);
}
return private;