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root@imx8qmmek:~# cat /sys/kernel/debug/regmap/5-0033/name [ 26.553924] Unable to handle kernel NULL pointer dereference at virtual address 00000000 [ 26.562052] pgd = ffff8008f779c000 [ 26.565457] [00000000] *pgd=000000096f40c003, *pud=0000000977872003, *pmd=0000000000000000 [ 26.573857] Internal error: Oops: 96000006 [#1] PREEMPT SMP [ 26.579436] Modules linked in: [ 26.582500] CPU: 3 PID: 3757 Comm: cat Not tainted 4.9.88-04623-g6be68dc123cc #1700 [ 26.590155] Hardware name: Freescale i.MX8QM MEK (DT) [ 26.595204] task: ffff8008ef513200 task.stack: ffff8008ef4e0000 [ 26.601142] PC is at regmap_name_read_file+0x54/0xa8 [ 26.606110] LR is at regmap_name_read_file+0x38/0xa8 [ 26.611076] pc : [] lr : [] pstate: 60000145 [ 26.618476] sp : ffff8008ef4e3d30 [ 26.621786] x29: ffff8008ef4e3d30 x28: ffff8008ef4e0000 [ 26.627111] x27: ffff000008c62000 x26: 000000000000003f [ 26.632437] x25: 0000000000000123 x24: ffff000008d6c710 [ 26.637762] x23: ffff8008ef4e3eb8 x22: 0000000000020000 [ 26.643087] x21: 0000ffff8ba60000 x20: ffff8008f72d2000 [ 26.648413] x19: ffff8008f6921800 x18: 000000000000037c [ 26.653738] x17: 0000000000418170 x16: ffff0000081dee00 [ 26.659064] x15: 0000ffff8ba84d00 x14: 0000ffff8ba91d98 [ 26.664389] x13: 000000000000270f x12: 0000000000000001 [ 26.669714] x11: 0000000000000000 x10: 0101010101010101 [ 26.675040] x9 : 0000000000000200 x8 : 00000000c00000b7 [ 26.680365] x7 : 0000000000000000 x6 : ffff8008ef41ee00 [ 26.685691] x5 : 00008008f6ce5000 x4 : ffff000009402000 [ 26.691016] x3 : 0000000000000000 x2 : ffff00000906d728 [ 26.696342] x1 : 0000000000001000 x0 : ffff8008f72d2000 [ 26.701667] So add check here. When the driver pointer is NULL, return -EIO. Signed-off-by: Peng Fan --- drivers/base/regmap/regmap-debugfs.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/base/regmap/regmap-debugfs.c b/drivers/base/regmap/regmap-debugfs.c index f3266334063e..d1097306d2ab 100644 --- a/drivers/base/regmap/regmap-debugfs.c +++ b/drivers/base/regmap/regmap-debugfs.c @@ -43,6 +43,9 @@ static ssize_t regmap_name_read_file(struct file *file, int ret; char *buf; + if (!map->dev->driver) + return -EIO; + buf = kmalloc(PAGE_SIZE, GFP_KERNEL); if (!buf) return -ENOMEM; -- 2.14.1