@samitouri / QOSamiQemu / commits / c96f6d2398

hw/9pfs: fix data race in v9fs_mark_fids_unreclaim()

A data race between v9fs_mark_fids_unreclaim() and v9fs_path_copy() causes an inconsistent read of fidp->path. In v9fs_path_copy(), the path size is set before the data pointer is allocated, creating a window where size is non-zero but data is NULL. v9fs_co_open2() holds a write lock during path modifications, but v9fs_mark_fids_unreclaim() was not acquiring a read lock, allowing it to race. Fix by holding the path read lock during FID table iteration. Resolves: https://gitlab.com/qemu-project/qemu/-/issues/3300 Signed-off-by: Richie Buturla <richie@linux.ibm.com> Link: https://lore.kernel.org/qemu-devel/20260211154450.254338-1-richie@linux.ibm.com/ Fixes: 7a46274529 ("hw/9pfs: Add file descriptor reclaim support") Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>

Richie Buturla committed Feb 11, 2026 at 16:44 UTC c96f6d2398a9dc068fa82088ea43020a52e2b26d

1 file changed +2

hw/9pfs/9p.c

@@ -560,6 +560,7 @@ static int coroutine_fn v9fs_mark_fids_unreclaim(V9fsPDU *pdu, V9fsPath *path)

560 sizeof(V9fsFidState *), 1);

561 gint i;

562

563 + v9fs_path_read_lock(s);

564 g_hash_table_iter_init(&iter, s->fids);

565

566 /*

@@ -580,6 +581,7 @@ static int coroutine_fn v9fs_mark_fids_unreclaim(V9fsPDU *pdu, V9fsPath *path)

581 g_array_append_val(to_reopen, fidp);

582 }

583 }

584 + v9fs_path_unlock(s);

585

586 for (i = 0; i < to_reopen->len; i++) {

587 fidp = g_array_index(to_reopen, V9fsFidState*, i);