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SubjectRe: [PATCH 5.6] io_uring: NULL-deref for IOSQE_{ASYNC,DRAIN}
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On 13/03/2020 23:28, Pavel Begunkov wrote:
> Hmm, found unreliably failing the across-fork test. I don't know whether it's
> this patch specific, but need to take a look there first.

It's good to go, just used outdated tests.
The reproducer is attached.

>
>>
>> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
>> ---
>> fs/io_uring.c | 8 ++++++++
>> 1 file changed, 8 insertions(+)
>>
>> diff --git a/fs/io_uring.c b/fs/io_uring.c
>> index 55afae6f0cf4..9d43efbec960 100644
>> --- a/fs/io_uring.c
>> +++ b/fs/io_uring.c
>> @@ -4813,6 +4813,9 @@ static int io_req_defer_prep(struct io_kiocb *req,
>> {
>> ssize_t ret = 0;
>>
>> + if (!sqe)
>> + return 0;
>> +
>> if (io_op_defs[req->opcode].file_table) {
>> ret = io_grab_files(req);
>> if (unlikely(ret))
>> @@ -5655,6 +5658,11 @@ static bool io_submit_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe,
>> if (sqe_flags & (IOSQE_IO_LINK|IOSQE_IO_HARDLINK)) {
>> req->flags |= REQ_F_LINK;
>> INIT_LIST_HEAD(&req->link_list);
>> +
>> + if (io_alloc_async_ctx(req)) {
>> + ret = -EAGAIN;
>> + goto err_req;
>> + }
>> ret = io_req_defer_prep(req, sqe);
>> if (ret)
>> req->flags |= REQ_F_FAIL_LINK;
>>
>

--
Pavel Begunkov
#include <errno.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/poll.h>
#include <sys/eventfd.h>
#include "liburing.h"

#define BS 4096
static struct iovec vecs[1];
static int no_read;

static int create_file(const char *file)
{
ssize_t ret;
char *buf;
int fd;

buf = malloc(BS);
memset(buf, 0xaa, BS);

fd = open(file, O_WRONLY | O_CREAT, 0644);
if (fd < 0) {
perror("open file");
return 1;
}
ret = write(fd, buf, BS);
close(fd);
return ret != BS;
}


static int create_buffers(void)
{
if (posix_memalign(&vecs[0].iov_base, BS, BS))
return 1;
vecs[0].iov_len = BS;
return 0;
}

static int test_io(const char *file)
{
const int nr_links = 100;
const int link_len = 100;
const int nr_sqes = nr_links * link_len;
struct io_uring_sqe *sqe;
struct io_uring_cqe *cqe;
struct io_uring ring;
int i, fd, ret;
static int warned;

fd = open(file, O_WRONLY);
if (fd < 0) {
perror("file open");
goto err;
}

ret = io_uring_queue_init(nr_sqes, &ring, 0);
if (ret) {
fprintf(stderr, "ring create failed: %d\n", ret);
goto err;
}

for (int i = 0; i < nr_links; ++i) {
for (int j = 0; j < link_len; ++j) {
sqe = io_uring_get_sqe(&ring);
if (!sqe) {
fprintf(stderr, "sqe get failed\n");
goto err;
}
io_uring_prep_writev(sqe, fd, &vecs[0], 1, 0);
sqe->flags |= IOSQE_ASYNC;
if (j != link_len - 1)
sqe->flags |= IOSQE_IO_LINK;
}
}

ret = io_uring_submit(&ring);
if (ret != nr_sqes) {
fprintf(stderr, "submit got %d, wanted %d\n", ret, nr_sqes);
goto err;
}

for (i = 0; i < nr_sqes; i++) {
ret = io_uring_wait_cqe(&ring, &cqe);
if (ret) {
fprintf(stderr, "wait_cqe=%d\n", ret);
goto err;
}
if (cqe->res == -EINVAL) {
if (!warned) {
fprintf(stdout, "Non-vectored IO not "
"supported, skipping\n");
warned = 1;
no_read = 1;
}
} else if (cqe->res != BS) {
fprintf(stderr, "cqe res %d, wanted %d\n", cqe->res, BS);
goto err;
}
io_uring_cqe_seen(&ring, cqe);
}

io_uring_queue_exit(&ring);
close(fd);
return 0;
err:
if (fd != -1)
close(fd);
return 1;
}

int main(int argc, char *argv[])
{
if (create_file(".basic-rw")) {
fprintf(stderr, "file creation failed\n");
goto err;
}
if (create_buffers()) {
fprintf(stderr, "file creation failed\n");
goto err;
}


test_io(".basic-rw");
unlink(".basic-rw");
return 0;
err:
unlink(".basic-rw");
return 1;
}
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