From: Vimal Agrawal vimal.agrawal@sophos.com

misc_minor_alloc was allocating id using ida for minor only in case of MISC_DYNAMIC_MINOR but misc_minor_free was always freeing ids using ida_free causing a mismatch and following warn:

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WARNING: CPU: 0 PID: 159 at lib/idr.c:525 ida_free+0x3e0/0x41f ida_free called for id=127 which is not allocated. <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<

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[<60941eb4>] ida_free+0x3e0/0x41f [<605ac993>] misc_minor_free+0x3e/0xbc [<605acb82>] misc_deregister+0x171/0x1b3

misc_minor_alloc is changed to allocate id from ida for all minors falling in the range of dynamic/ misc dynamic minors

Fixes: ab760791c0cf ("char: misc: Increase the maximum number of dynamic misc devices to 1048448") Signed-off-by: Vimal Agrawal vimal.agrawal@sophos.com Reviewed-by: Dirk VanDerMerwe dirk.vandermerwe@sophos.com Cc: stable@vger.kernel.org --- v2: Added Fixes: Added missed case for static minor in misc_minor_alloc v3: Removed kunit changes as that will be added as second patch in this two patch series v4: Updated Signed-off-by: to match from: v5: Used corporate id in from: and Signed-off-by:

drivers/char/misc.c | 39 ++++++++++++++++++++++++++++++--------- 1 file changed, 30 insertions(+), 9 deletions(-)

diff --git a/drivers/char/misc.c b/drivers/char/misc.c index 541edc26ec89..2cf595d2e10b 100644 --- a/drivers/char/misc.c +++ b/drivers/char/misc.c @@ -63,16 +63,30 @@ static DEFINE_MUTEX(misc_mtx); #define DYNAMIC_MINORS 128 /* like dynamic majors */ static DEFINE_IDA(misc_minors_ida);

-static int misc_minor_alloc(void) +static int misc_minor_alloc(int minor) { - int ret; - - ret = ida_alloc_max(&misc_minors_ida, DYNAMIC_MINORS - 1, GFP_KERNEL); - if (ret >= 0) { - ret = DYNAMIC_MINORS - ret - 1; + int ret = 0; + + if (minor == MISC_DYNAMIC_MINOR) { + /* allocate free id */ + ret = ida_alloc_max(&misc_minors_ida, DYNAMIC_MINORS - 1, GFP_KERNEL); + if (ret >= 0) { + ret = DYNAMIC_MINORS - ret - 1; + } else { + ret = ida_alloc_range(&misc_minors_ida, MISC_DYNAMIC_MINOR + 1, + MINORMASK, GFP_KERNEL); + } } else { - ret = ida_alloc_range(&misc_minors_ida, MISC_DYNAMIC_MINOR + 1, - MINORMASK, GFP_KERNEL); + /* specific minor, check if it is in dynamic or misc dynamic range */ + if (minor < DYNAMIC_MINORS) { + minor = DYNAMIC_MINORS - minor - 1; + ret = ida_alloc_range(&misc_minors_ida, minor, minor, GFP_KERNEL); + } else if (minor > MISC_DYNAMIC_MINOR) { + ret = ida_alloc_range(&misc_minors_ida, minor, minor, GFP_KERNEL); + } else { + /* case of non-dynamic minors, no need to allocate id */ + ret = 0; + } } return ret; } @@ -219,7 +233,7 @@ int misc_register(struct miscdevice *misc) mutex_lock(&misc_mtx);

if (is_dynamic) { - int i = misc_minor_alloc(); + int i = misc_minor_alloc(misc->minor);

if (i < 0) { err = -EBUSY; @@ -228,6 +242,7 @@ int misc_register(struct miscdevice *misc) misc->minor = i; } else { struct miscdevice *c; + int i;

list_for_each_entry(c, &misc_list, list) { if (c->minor == misc->minor) { @@ -235,6 +250,12 @@ int misc_register(struct miscdevice *misc) goto out; } } + + i = misc_minor_alloc(misc->minor); + if (i < 0) { + err = -EBUSY; + goto out; + } }

dev = MKDEV(MISC_MAJOR, misc->minor);