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af_unix: Don't peek OOB data without MSG_OOB.
[ Upstream commit 22dd70eb2c3d754862964377a75abafd3167346b ] Currently, we can read OOB data without MSG_OOB by using MSG_PEEK when OOB data is sitting on the front row, which is apparently wrong. >>> from socket import * >>> c1, c2 = socketpair(AF_UNIX, SOCK_STREAM) >>> c1.send(b'a', MSG_OOB) 1 >>> c2.recv(1, MSG_PEEK | MSG_DONTWAIT) b'a' If manage_oob() is called when no data has been copied, we only check if the socket enables SO_OOBINLINE or MSG_PEEK is not used. Otherwise, the skb is returned as is. However, here we should return NULL if MSG_PEEK is set and no data has been copied. Also, in such a case, we should not jump to the redo label because we will be caught in the loop and hog the CPU until normal data comes in. Then, we need to handle skb == NULL case with the if-clause below the manage_oob() block. With this patch: >>> from socket import * >>> c1, c2 = socketpair(AF_UNIX, SOCK_STREAM) >>> c1.send(b'a', MSG_OOB) 1 >>> c2.recv(1, MSG_PEEK | MSG_DONTWAIT) Traceback (most recent call last): File "<stdin>", line 1, in <module> BlockingIOError: [Errno 11] Resource temporarily unavailable Fixes: 314001f ("af_unix: Add OOB support") Signed-off-by: Kuniyuki Iwashima <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Jakub Kicinski <[email protected]> Signed-off-by: Sasha Levin <[email protected]>
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