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Muhammet Kaan KILINÇ
7b91e51d0e
The AIO/async path in skcipher_recvmsg() passes the socket-wide ctx->iv directly into the skcipher request. After io_submit() the socket lock is dropped and the request is processed asynchronously, so a concurrent sendmsg(ALG_SET_IV) can overwrite ctx->iv and make the in-flight request run under an attacker-controlled IV. For CTR/stream modes this is IV/keystream reuse and lets an unprivileged user recover the plaintext of a concurrent operation. Snapshotting ctx->iv into per-request storage for the async path is not sufficient. For ciphers with statesize == 0 - which includes cbc and ctr - the MSG_MORE inter-chunk IV chaining is carried solely by the in-place req->iv writeback, which a snapshot redirects into per-request memory that af_alg_free_resources() releases on completion, silently producing wrong output. Writing the IV back from the completion callback instead is not possible either: that would require lock_sock() there, but the callback can run in softirq/atomic context, so it must not sleep. Make the operation synchronous instead, which removes both the IV race and any writeback race. This is equivalent to the upstream resolution, commitfcc77d33a3("net: Remove support for AIO on sockets"), which removed the AIO socket path across net/ entirely and so produces the same end state for this file. This patch deviates from that commit deliberately: rather than removing AIO socket support tree-wide, which would be far too invasive for stable, it removes only the AIO branch in crypto/algif_skcipher.c. io_submit() now completes synchronously; AF_ALG async is rarely used in practice. The -EIOCBQUEUED check in skcipher_recvmsg() is now dead but harmless, and is left alone to keep the fix minimal. Tested on 6.6.y: attacker IV injection dropped from 2296/200000 to 0/200000 after the change; MSG_MORE chunked CTR output bit-identical to single-shot. Reported-by: Muhammet Kaan KILINÇ <muhammetkaankilinc@gmail.com> Fixes:e870456d8e("crypto: algif_skcipher - overhaul memory management") Cc: <stable@vger.kernel.org> Signed-off-by: Muhammet Kaan KILINÇ <muhammetkaankilinc@gmail.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
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