From: Zhiqiang Liu liuzhiqiang26@huawei.com
[ Upstream commit c8ab422553c81a0eb070329c63725df1cd1425bc ]
In brd_init func, rd_nr num of brd_device are firstly allocated and add in brd_devices, then brd_devices are traversed to add each brd_device by calling add_disk func. When allocating brd_device, the disk->first_minor is set to i * max_part, if rd_nr * max_part is larger than MINORMASK, two different brd_device may have the same devt, then only one of them can be successfully added. when rmmod brd.ko, it will cause oops when calling brd_exit.
Follow those steps: # modprobe brd rd_nr=3 rd_size=102400 max_part=1048576 # rmmod brd then, the oops will appear.
Oops log: [ 726.613722] Call trace: [ 726.614175] kernfs_find_ns+0x24/0x130 [ 726.614852] kernfs_find_and_get_ns+0x44/0x68 [ 726.615749] sysfs_remove_group+0x38/0xb0 [ 726.616520] blk_trace_remove_sysfs+0x1c/0x28 [ 726.617320] blk_unregister_queue+0x98/0x100 [ 726.618105] del_gendisk+0x144/0x2b8 [ 726.618759] brd_exit+0x68/0x560 [brd] [ 726.619501] __arm64_sys_delete_module+0x19c/0x2a0 [ 726.620384] el0_svc_common+0x78/0x130 [ 726.621057] el0_svc_handler+0x38/0x78 [ 726.621738] el0_svc+0x8/0xc [ 726.622259] Code: aa0203f6 aa0103f7 aa1e03e0 d503201f (7940e260)
Here, we add brd_check_and_reset_par func to check and limit max_part par.
-- V5->V6: - remove useless code
V4->V5:(suggested by Ming Lei) - make sure max_part is not larger than DISK_MAX_PARTS
V3->V4:(suggested by Ming Lei) - remove useless change - add one limit of max_part
V2->V3: (suggested by Ming Lei) - clear .minors when running out of consecutive minor space in brd_alloc - remove limit of rd_nr
V1->V2: - add more checks in brd_check_par_valid as suggested by Ming Lei.
Signed-off-by: Zhiqiang Liu liuzhiqiang26@huawei.com Reviewed-by: Bob Liu bob.liu@oracle.com Reviewed-by: Ming Lei ming.lei@redhat.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/block/brd.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-)
diff --git a/drivers/block/brd.c b/drivers/block/brd.c index 0c76d4016eebe..7e35574a17dfc 100644 --- a/drivers/block/brd.c +++ b/drivers/block/brd.c @@ -581,6 +581,25 @@ static struct kobject *brd_probe(dev_t dev, int *part, void *data) return kobj; }
+static inline void brd_check_and_reset_par(void) +{ + if (unlikely(!max_part)) + max_part = 1; + + /* + * make sure 'max_part' can be divided exactly by (1U << MINORBITS), + * otherwise, it is possiable to get same dev_t when adding partitions. + */ + if ((1U << MINORBITS) % max_part != 0) + max_part = 1UL << fls(max_part); + + if (max_part > DISK_MAX_PARTS) { + pr_info("brd: max_part can't be larger than %d, reset max_part = %d.\n", + DISK_MAX_PARTS, DISK_MAX_PARTS); + max_part = DISK_MAX_PARTS; + } +} + static int __init brd_init(void) { struct brd_device *brd, *next; @@ -604,8 +623,7 @@ static int __init brd_init(void) if (register_blkdev(RAMDISK_MAJOR, "ramdisk")) return -EIO;
- if (unlikely(!max_part)) - max_part = 1; + brd_check_and_reset_par();
for (i = 0; i < rd_nr; i++) { brd = brd_alloc(i);