5.4-stable review patch. If anyone has any objections, please let me know.
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From: Jeongjun Park aha310510@gmail.com
commit d66adabe91803ef34a8b90613c81267b5ded1472 upstream.
syzbot reported that it discovered a use-after-free vulnerability, [0]
[0]: https://lore.kernel.org/all/67af13f8.050a0220.21dd3.0038.GAE@google.com/
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/20250424143322.18830-1-aha310510@gmail.com Fixes: b34a6b1da371 ("ipc: introduce shm_rmid_forced sysctl") Signed-off-by: Jeongjun Park aha310510@gmail.com Reported-by: syzbot+a2b84e569d06ca3a949c@syzkaller.appspotmail.com Cc: Jeongjun Park aha310510@gmail.com Cc: Liam Howlett liam.howlett@oracle.com Cc: Lorenzo Stoakes lorenzo.stoakes@oracle.com Cc: Matthew Wilcox (Oracle) willy@infradead.org Cc: Vasiliy Kulikov segoon@openwall.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- ipc/shm.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
--- a/ipc/shm.c +++ b/ipc/shm.c @@ -417,8 +417,11 @@ static int shm_try_destroy_orphaned(int 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); }