linux/io_uring/msg_ring.c
Harshit Mogalapalli 16bbdfe5fb io_uring/msg_ring: Fix NULL pointer dereference in io_msg_send_fd()
Syzkaller produced the below call trace:

 BUG: KASAN: null-ptr-deref in io_msg_ring+0x3cb/0x9f0
 Write of size 8 at addr 0000000000000070 by task repro/16399

 CPU: 0 PID: 16399 Comm: repro Not tainted 6.1.0-rc1 #28
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.el7
 Call Trace:
  <TASK>
  dump_stack_lvl+0xcd/0x134
  ? io_msg_ring+0x3cb/0x9f0
  kasan_report+0xbc/0xf0
  ? io_msg_ring+0x3cb/0x9f0
  kasan_check_range+0x140/0x190
  io_msg_ring+0x3cb/0x9f0
  ? io_msg_ring_prep+0x300/0x300
  io_issue_sqe+0x698/0xca0
  io_submit_sqes+0x92f/0x1c30
  __do_sys_io_uring_enter+0xae4/0x24b0
....
 RIP: 0033:0x7f2eaf8f8289
 RSP: 002b:00007fff40939718 EFLAGS: 00000246 ORIG_RAX: 00000000000001aa
 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f2eaf8f8289
 RDX: 0000000000000000 RSI: 0000000000006f71 RDI: 0000000000000004
 RBP: 00007fff409397a0 R08: 0000000000000000 R09: 0000000000000039
 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004006d0
 R13: 00007fff40939880 R14: 0000000000000000 R15: 0000000000000000
  </TASK>
 Kernel panic - not syncing: panic_on_warn set ...

We don't have a NULL check on file_ptr in io_msg_send_fd() function,
so when file_ptr is NUL src_file is also NULL and get_file()
dereferences a NULL pointer and leads to above crash.

Add a NULL check to fix this issue.

Fixes: e6130eba8a ("io_uring: add support for passing fixed file descriptors")
Reported-by: syzkaller <syzkaller@googlegroups.com>
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Link: https://lore.kernel.org/r/20221019171218.1337614-1-harshit.m.mogalapalli@oracle.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-10-19 12:33:33 -07:00

176 lines
4.1 KiB
C

// SPDX-License-Identifier: GPL-2.0
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/file.h>
#include <linux/slab.h>
#include <linux/nospec.h>
#include <linux/io_uring.h>
#include <uapi/linux/io_uring.h>
#include "io_uring.h"
#include "rsrc.h"
#include "filetable.h"
#include "msg_ring.h"
struct io_msg {
struct file *file;
u64 user_data;
u32 len;
u32 cmd;
u32 src_fd;
u32 dst_fd;
u32 flags;
};
static int io_msg_ring_data(struct io_kiocb *req)
{
struct io_ring_ctx *target_ctx = req->file->private_data;
struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
if (msg->src_fd || msg->dst_fd || msg->flags)
return -EINVAL;
if (io_post_aux_cqe(target_ctx, msg->user_data, msg->len, 0, true))
return 0;
return -EOVERFLOW;
}
static void io_double_unlock_ctx(struct io_ring_ctx *ctx,
struct io_ring_ctx *octx,
unsigned int issue_flags)
{
if (issue_flags & IO_URING_F_UNLOCKED)
mutex_unlock(&ctx->uring_lock);
mutex_unlock(&octx->uring_lock);
}
static int io_double_lock_ctx(struct io_ring_ctx *ctx,
struct io_ring_ctx *octx,
unsigned int issue_flags)
{
/*
* To ensure proper ordering between the two ctxs, we can only
* attempt a trylock on the target. If that fails and we already have
* the source ctx lock, punt to io-wq.
*/
if (!(issue_flags & IO_URING_F_UNLOCKED)) {
if (!mutex_trylock(&octx->uring_lock))
return -EAGAIN;
return 0;
}
/* Always grab smallest value ctx first. We know ctx != octx. */
if (ctx < octx) {
mutex_lock(&ctx->uring_lock);
mutex_lock(&octx->uring_lock);
} else {
mutex_lock(&octx->uring_lock);
mutex_lock(&ctx->uring_lock);
}
return 0;
}
static int io_msg_send_fd(struct io_kiocb *req, unsigned int issue_flags)
{
struct io_ring_ctx *target_ctx = req->file->private_data;
struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
struct io_ring_ctx *ctx = req->ctx;
unsigned long file_ptr;
struct file *src_file;
int ret;
if (target_ctx == ctx)
return -EINVAL;
ret = io_double_lock_ctx(ctx, target_ctx, issue_flags);
if (unlikely(ret))
return ret;
ret = -EBADF;
if (unlikely(msg->src_fd >= ctx->nr_user_files))
goto out_unlock;
msg->src_fd = array_index_nospec(msg->src_fd, ctx->nr_user_files);
file_ptr = io_fixed_file_slot(&ctx->file_table, msg->src_fd)->file_ptr;
if (!file_ptr)
goto out_unlock;
src_file = (struct file *) (file_ptr & FFS_MASK);
get_file(src_file);
ret = __io_fixed_fd_install(target_ctx, src_file, msg->dst_fd);
if (ret < 0) {
fput(src_file);
goto out_unlock;
}
if (msg->flags & IORING_MSG_RING_CQE_SKIP)
goto out_unlock;
/*
* If this fails, the target still received the file descriptor but
* wasn't notified of the fact. This means that if this request
* completes with -EOVERFLOW, then the sender must ensure that a
* later IORING_OP_MSG_RING delivers the message.
*/
if (!io_post_aux_cqe(target_ctx, msg->user_data, msg->len, 0, true))
ret = -EOVERFLOW;
out_unlock:
io_double_unlock_ctx(ctx, target_ctx, issue_flags);
return ret;
}
int io_msg_ring_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
if (unlikely(sqe->buf_index || sqe->personality))
return -EINVAL;
msg->user_data = READ_ONCE(sqe->off);
msg->len = READ_ONCE(sqe->len);
msg->cmd = READ_ONCE(sqe->addr);
msg->src_fd = READ_ONCE(sqe->addr3);
msg->dst_fd = READ_ONCE(sqe->file_index);
msg->flags = READ_ONCE(sqe->msg_ring_flags);
if (msg->flags & ~IORING_MSG_RING_CQE_SKIP)
return -EINVAL;
return 0;
}
int io_msg_ring(struct io_kiocb *req, unsigned int issue_flags)
{
struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
int ret;
ret = -EBADFD;
if (!io_is_uring_fops(req->file))
goto done;
switch (msg->cmd) {
case IORING_MSG_DATA:
ret = io_msg_ring_data(req);
break;
case IORING_MSG_SEND_FD:
ret = io_msg_send_fd(req, issue_flags);
break;
default:
ret = -EINVAL;
break;
}
done:
if (ret < 0)
req_set_fail(req);
io_req_set_res(req, ret, 0);
/* put file to avoid an attempt to IOPOLL the req */
if (!(req->flags & REQ_F_FIXED_FILE))
io_put_file(req->file);
req->file = NULL;
return IOU_OK;
}