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ipc: fix to protect IPCS lookups using RCU

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commit d66adabe91803ef34a8b90613c81267b5ded1472 upstream.

syzbot reported that it discovered a use-after-free vulnerability, [0]

[0]: https://lore.kernel.org/all/[email protected]/

idr_for_each() is protected by rwsem, but this is not enough.  If it is
not protected by RCU read-critical region, when idr_for_each() calls
radix_tree_node_free() through call_rcu() to free the radix_tree_node
structure, the node will be freed immediately, and when reading the next
node in radix_tree_for_each_slot(), the already freed memory may be read.

Therefore, we need to add code to make sure that idr_for_each() is
protected within the RCU read-critical region when we call it in
shm_destroy_orphaned().

Link: https://lkml.kernel.org/r/[email protected]
Fixes: b34a6b1da3 ("ipc: introduce shm_rmid_forced sysctl")
Signed-off-by: Jeongjun Park <[email protected]>
Reported-by: [email protected]
Cc: Jeongjun Park <[email protected]>
Cc: Liam Howlett <[email protected]>
Cc: Lorenzo Stoakes <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Vasiliy Kulikov <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
This commit is contained in:
Jeongjun Park 2025-04-24 23:33:22 +09:00 • committed by Greg Kroah-Hartman
commit 5f1e1573bf
1 changed files with 4 additions and 1 deletions
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5
ipc/shm.c
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@ -417,8 +417,11 @@ static int shm_try_destroy_orphaned(int id, void *p, void *data)
void shm_destroy_orphaned(struct ipc_namespace *ns)
{
down_write(&shm_ids(ns).rwsem);
if (shm_ids(ns).in_use)
if (shm_ids(ns).in_use) {
rcu_read_lock();
idr_for_each(&shm_ids(ns).ipcs_idr, &shm_try_destroy_orphaned, ns);
rcu_read_unlock();
}
up_write(&shm_ids(ns).rwsem);
}