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authorJens Axboe <axboe@kernel.dk>2019-05-14 20:00:30 -0600
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-06-15 11:53:06 +0200
commitcf1fa8c91fbd1111782bac82cdd01b6330bfbbca (patch)
tree25e4c73a1a561ddaaa0f0e4d477d195b18dc08c4
parentbc9dcb27e9dfbddcb8e1627e509b4e4b637c4415 (diff)
io_uring: fix failure to verify SQ_AFF cpu
commit 44a9bd18a0f06bba19d155aeaa11e2edce898293 upstream. The test case we have is rightfully failing with the current kernel: io_uring_setup(1, 0x7ffe2cafebe0), flags: IORING_SETUP_SQPOLL|IORING_SETUP_SQ_AFF, resv: 0x00000000 0x00000000 0x00000000 0x00000000 0x00000000, sq_thread_cpu: 4 expected -1, got 3 This is in a vm, and CPU3 is the last valid one, hence asking for 4 should fail the setup with -EINVAL, not succeed. The problem is that we're using array_index_nospec() with nr_cpu_ids as the index, hence we wrap and end up using CPU0 instead of CPU4. This makes the setup succeed where it should be failing. We don't need to use array_index_nospec() as we're not indexing any array with this. Instead just compare with nr_cpu_ids directly. This is fine as we're checking with cpu_online() afterwards. Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--fs/io_uring.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 30a5687a17b6..28269a0c5037 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2330,10 +2330,11 @@ static int io_sq_offload_start(struct io_ring_ctx *ctx,
ctx->sq_thread_idle = HZ;
if (p->flags & IORING_SETUP_SQ_AFF) {
- int cpu = array_index_nospec(p->sq_thread_cpu,
- nr_cpu_ids);
+ int cpu = p->sq_thread_cpu;
ret = -EINVAL;
+ if (cpu >= nr_cpu_ids)
+ goto err;
if (!cpu_online(cpu))
goto err;