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Subject[PATCH AUTOSEL 5.4 07/18] nvme-core: get/put ctrl and transport module in nvme_dev_open/release()
Date
From: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>

[ Upstream commit 52a3974feb1a3eec25d8836d37a508b67b0a9cd0 ]

Get and put the reference to the ctrl in the nvme_dev_open() and
nvme_dev_release() before and after module get/put for ctrl in char
device file operations.

Introduce char_dev relase function, get/put the controller and module
which allows us to fix the potential Oops which can be easily reproduced
with a passthru ctrl (although the problem also exists with pure user
access):

Entering kdb (current=0xffff8887f8290000, pid 3128) on processor 30 Oops: (null)
due to oops @ 0xffffffffa01019ad
CPU: 30 PID: 3128 Comm: bash Tainted: G W OE 5.8.0-rc4nvme-5.9+ #35
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.4
RIP: 0010:nvme_free_ctrl+0x234/0x285 [nvme_core]
Code: 57 10 a0 e8 73 bf 02 e1 ba 3d 11 00 00 48 c7 c6 98 33 10 a0 48 c7 c7 1d 57 10 a0 e8 5b bf 02 e1 8
RSP: 0018:ffffc90001d63de0 EFLAGS: 00010246
RAX: ffffffffa05c0440 RBX: ffff8888119e45a0 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff8888177e9550 RDI: ffff8888119e43b0
RBP: ffff8887d4768000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: ffffc90001d63c90 R12: ffff8888119e43b0
R13: ffff8888119e5108 R14: dead000000000100 R15: ffff8888119e5108
FS: 00007f1ef27b0740(0000) GS:ffff888817600000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffa05c0470 CR3: 00000007f6bee000 CR4: 00000000003406e0
Call Trace:
device_release+0x27/0x80
kobject_put+0x98/0x170
nvmet_passthru_ctrl_disable+0x4a/0x70 [nvmet]
nvmet_passthru_enable_store+0x4c/0x90 [nvmet]
configfs_write_file+0xe6/0x150
vfs_write+0xba/0x1e0
ksys_write+0x5f/0xe0
do_syscall_64+0x52/0xb0
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7f1ef1eb2840
Code: Bad RIP value.
RSP: 002b:00007fffdbff0eb8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007f1ef1eb2840
RDX: 0000000000000002 RSI: 00007f1ef27d2000 RDI: 0000000000000001
RBP: 00007f1ef27d2000 R08: 000000000000000a R09: 00007f1ef27b0740
R10: 0000000000000001 R11: 0000000000000246 R12: 00007f1ef2186400
R13: 0000000000000002 R14: 0000000000000001 R15: 0000000000000000

With this patch fix we take the module ref count in nvme_dev_open() and
release that ref count in newly introduced nvme_dev_release().

Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/nvme/host/core.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 2d2673d360ff2..a8df939f50b87 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -2936,10 +2936,24 @@ static int nvme_dev_open(struct inode *inode, struct file *file)
return -EWOULDBLOCK;
}

+ nvme_get_ctrl(ctrl);
+ if (!try_module_get(ctrl->ops->module))
+ return -EINVAL;
+
file->private_data = ctrl;
return 0;
}

+static int nvme_dev_release(struct inode *inode, struct file *file)
+{
+ struct nvme_ctrl *ctrl =
+ container_of(inode->i_cdev, struct nvme_ctrl, cdev);
+
+ module_put(ctrl->ops->module);
+ nvme_put_ctrl(ctrl);
+ return 0;
+}
+
static int nvme_dev_user_cmd(struct nvme_ctrl *ctrl, void __user *argp)
{
struct nvme_ns *ns;
@@ -3002,6 +3016,7 @@ static long nvme_dev_ioctl(struct file *file, unsigned int cmd,
static const struct file_operations nvme_dev_fops = {
.owner = THIS_MODULE,
.open = nvme_dev_open,
+ .release = nvme_dev_release,
.unlocked_ioctl = nvme_dev_ioctl,
.compat_ioctl = nvme_dev_ioctl,
};
--
2.25.1
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