rpmsg: char: Check for ongoing chrdev destroy

A null pointer panic is observed when stopping a remoteproc and closing
a character device using the RPMSG_DESTROY_EPT_IOCTL. There is a race
where each context calls rpmsg_chrdev_eptdev_destroy(). The thread that
runs second will call cdev_device_del() for a second time, which fails
because the first call already removed the device from sysfs. Add a
check at the beginning of destroy and exit early if the destroy call
has already been done.

[ 26.654130] Call trace
[ 26.656658] kernfs_find_and_get_ns+0x28/0x8
[ 26.661140] sysfs_unmerge_group+0x2c/0x7
[ 26.665357] dpm_sysfs_remove+0x38/0x8
[ 26.669305] device_del+0xa4/0x3e
[ 26.672811] cdev_device_del+0x28/0x7
[ 26.676675] rpmsg_chrdev_eptdev_destroy+0x68/0x98
[ 26.682765] rpmsg_eptdev_ioctl+0x130/0x11c8
[ 26.688318] __arm64_sys_ioctl+0xb4/0x10
[ 26.692448] invoke_syscall+0x50/0x12
[ 26.696312] el0_svc_common.constprop.0+0xc8/0xf
[ 26.701151] do_el0_svc+0x24/0x3
[ 26.704570] el0_svc+0x40/0x17
[ 26.707810] el0t_64_sync_handler+0x120/0x13
[ 26.712288] el0t_64_sync+0x1a0/0x1a

Signed-off-by: Chris Lew <christopher.lew@oss.qualcomm.com>
Signed-off-by: Vishnu Santhosh <vishnu.santhosh@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20260406-rpmsg-char-fix-chrdev-destroy-race-v1-1-7317434fa246@oss.qualcomm.com
Signed-off-by: Bjorn Andersson <andersson@kernel.org>

0 files changed, 0 insertions, 0 deletions