[PATCH] io_uring: Fix NULL pointer dereference in loop_rw_iter()
From: Guoyu Huang
Date: Wed Aug 05 2020 - 15:56:50 EST
loop_rw_iter() does not check whether the file has a read or
write function. This can lead to NULL pointer dereference
when the user passes in a file descriptor that does not have
read or write function.
The crash log looks like this:
[ 99.834071] BUG: kernel NULL pointer dereference, address: 0000000000000000
[ 99.835364] #PF: supervisor instruction fetch in kernel mode
[ 99.836522] #PF: error_code(0x0010) - not-present page
[ 99.837771] PGD 8000000079d62067 P4D 8000000079d62067 PUD 79d8c067 PMD 0
[ 99.839649] Oops: 0010 [#2] SMP PTI
[ 99.840591] CPU: 1 PID: 333 Comm: io_wqe_worker-0 Tainted: G D 5.8.0 #2
[ 99.842622] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1 04/01/2014
[ 99.845140] RIP: 0010:0x0
[ 99.845840] Code: Bad RIP value.
[ 99.846672] RSP: 0018:ffffa1c7c01ebc08 EFLAGS: 00010202
[ 99.848018] RAX: 0000000000000000 RBX: ffff92363bd67300 RCX: ffff92363d461208
[ 99.849854] RDX: 0000000000000010 RSI: 00007ffdbf696bb0 RDI: ffff92363bd67300
[ 99.851743] RBP: ffffa1c7c01ebc40 R08: 0000000000000000 R09: 0000000000000000
[ 99.853394] R10: ffffffff9ec692a0 R11: 0000000000000000 R12: 0000000000000010
[ 99.855148] R13: 0000000000000000 R14: ffff92363d461208 R15: ffffa1c7c01ebc68
[ 99.856914] FS: 0000000000000000(0000) GS:ffff92363dd00000(0000) knlGS:0000000000000000
[ 99.858651] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 99.860032] CR2: ffffffffffffffd6 CR3: 000000007ac66000 CR4: 00000000000006e0
[ 99.861979] Call Trace:
[ 99.862617] loop_rw_iter.part.0+0xad/0x110
[ 99.863838] io_write+0x2ae/0x380
[ 99.864644] ? kvm_sched_clock_read+0x11/0x20
[ 99.865595] ? sched_clock+0x9/0x10
[ 99.866453] ? sched_clock_cpu+0x11/0xb0
[ 99.867326] ? newidle_balance+0x1d4/0x3c0
[ 99.868283] io_issue_sqe+0xd8f/0x1340
[ 99.869216] ? __switch_to+0x7f/0x450
[ 99.870280] ? __switch_to_asm+0x42/0x70
[ 99.871254] ? __switch_to_asm+0x36/0x70
[ 99.872133] ? lock_timer_base+0x72/0xa0
[ 99.873155] ? switch_mm_irqs_off+0x1bf/0x420
[ 99.874152] io_wq_submit_work+0x64/0x180
[ 99.875192] ? kthread_use_mm+0x71/0x100
[ 99.876132] io_worker_handle_work+0x267/0x440
[ 99.877233] io_wqe_worker+0x297/0x350
[ 99.878145] kthread+0x112/0x150
[ 99.878849] ? __io_worker_unuse+0x100/0x100
[ 99.879935] ? kthread_park+0x90/0x90
[ 99.880874] ret_from_fork+0x22/0x30
[ 99.881679] Modules linked in:
[ 99.882493] CR2: 0000000000000000
[ 99.883324] ---[ end trace 4453745f4673190b ]---
[ 99.884289] RIP: 0010:0x0
[ 99.884837] Code: Bad RIP value.
[ 99.885492] RSP: 0018:ffffa1c7c01ebc08 EFLAGS: 00010202
[ 99.886851] RAX: 0000000000000000 RBX: ffff92363acd7f00 RCX: ffff92363d461608
[ 99.888561] RDX: 0000000000000010 RSI: 00007ffe040d9e10 RDI: ffff92363acd7f00
[ 99.890203] RBP: ffffa1c7c01ebc40 R08: 0000000000000000 R09: 0000000000000000
[ 99.891907] R10: ffffffff9ec692a0 R11: 0000000000000000 R12: 0000000000000010
[ 99.894106] R13: 0000000000000000 R14: ffff92363d461608 R15: ffffa1c7c01ebc68
[ 99.896079] FS: 0000000000000000(0000) GS:ffff92363dd00000(0000) knlGS:0000000000000000
[ 99.898017] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 99.899197] CR2: ffffffffffffffd6 CR3: 000000007ac66000 CR4: 00000000000006e0
Signed-off-by: Guoyu Huang <hgy5945@xxxxxxxxx>
---
fs/io_uring.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 493e5047e67c..3c21e2e002b4 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2661,8 +2661,10 @@ static int io_read(struct io_kiocb *req, bool force_nonblock)
if (req->file->f_op->read_iter)
ret2 = call_read_iter(req->file, kiocb, &iter);
- else
+ else if (req->file->f_op->read)
ret2 = loop_rw_iter(READ, req->file, kiocb, &iter);
+ else
+ ret2 = -EINVAL;
/* Catch -EAGAIN return for forced non-blocking submission */
if (!force_nonblock || ret2 != -EAGAIN) {
@@ -2776,8 +2778,10 @@ static int io_write(struct io_kiocb *req, bool force_nonblock)
if (req->file->f_op->write_iter)
ret2 = call_write_iter(req->file, kiocb, &iter);
- else
+ else if (req->file->f_op->write)
ret2 = loop_rw_iter(WRITE, req->file, kiocb, &iter);
+ else
+ ret2 = -EINVAL;
if (!force_nonblock)
current->signal->rlim[RLIMIT_FSIZE].rlim_cur = RLIM_INFINITY;
--
2.25.1