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