Hi, Is there any modification / improvement needed in this patch ?
------- Original Message ------- Sender : Shivnandan Kumar<[email protected]> Engineer/SRI-Noida-Advance Solutions - System 1 R&D Group/Samsung Electronics Date : Nov 20, 2015 15:35 (GMT+05:30) Title : [PATCH] char:misc minor is overflowing When a driver register as a misc driver and it tries to allocate minor number dynamically. Then there is a chance of minor number overflow. The problem is that 64(DYNAMIC_MINORS) is not enough for dynamic minor number and if kernel defines 0-63 for dynamic minor number, it should be reserved. But,0-10 was used for other devices, for example 1 is reserved for PSMOUSE. I got the issue that misc_minors is 0x3FFFFFFFFFFFFFFF and so, value of variable 'i' in function misc_register becomes 62 and so misc_minors become 1.(Which was already reserved for PSMOUSE). This patch help to avoid the above problem. Signed-off-by: shivnandan kumar --- drivers/char/misc.c | 5 ++--- include/linux/miscdevice.h | 1 + 2 files changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/char/misc.c b/drivers/char/misc.c index 8069b36..1a6a640 100644 --- a/drivers/char/misc.c +++ b/drivers/char/misc.c @@ -198,7 +198,7 @@ int misc_register(struct miscdevice * misc) err = -EBUSY; goto out; } - misc->minor = DYNAMIC_MINORS - i - 1; + misc->minor = DYNAMIC_MINORS - i - 1 + DYNAMIC_MINOR_START; set_bit(i, misc_minors); } else { struct miscdevice *c; @@ -218,8 +218,7 @@ int misc_register(struct miscdevice * misc) misc, misc->groups, "%s", misc->name); if (IS_ERR(misc->this_device)) { if (is_dynamic) { - int i = DYNAMIC_MINORS - misc->minor - 1; + int i = DYNAMIC_MINORS - misc->minor - 1 + DYNAMIC_MINOR_START; if (i < DYNAMIC_MINORS && i >= 0) clear_bit(i, misc_minors); misc->minor = MISC_DYNAMIC_MINOR; diff --git a/include/linux/miscdevice.h b/include/linux/miscdevice.h index 81f6e42..7aa931e 100644 --- a/include/linux/miscdevice.h +++ b/include/linux/miscdevice.h @@ -19,6 +19,7 @@ #define APOLLO_MOUSE_MINOR 7 /* unused */ #define PC110PAD_MINOR 9 /* unused */ /*#define ADB_MOUSE_MINOR 10 FIXME OBSOLETE */ +#define DYNAMIC_MINOR_START 11 #define WATCHDOG_MINOR 130 /* Watchdog timer */ #define TEMP_MINOR 131 /* Temperature Sensor */ #define RTC_MINOR 135 -- 1.7.9.5 Nitin Gupta Logix Cyber Park • Plot No. C 28-29, Tower D - Ground to 10th Floor, Tower C - 8th to 10th Floor, Sector 62 • Noida(U.P.) 201301 • INDIA
