diff options
| author | Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com> | 2015-05-18 20:11:46 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-06-01 00:38:21 +0300 |
| commit | b575f7124ab33b2a4239613bcc870380308fe0a7 (patch) | |
| tree | b8b35a0f055588f9e2f4361c601d8e01bc64c52d /drivers/char/misc.c | |
| parent | b144ce2d37619e05afdb0a15676500d76a64b1be (diff) | |
| download | linux-b575f7124ab33b2a4239613bcc870380308fe0a7.tar.xz | |
char: misc: restore MISC_DYNAMIC_MINOR on device_create() failure
On attempt to register a dynamic minor misc device its minor number is
updated to a virtual minor number prior to device_create() call,
however on error path misc->minor == MISC_DYNAMIC_MINOR is not
restored.
Following the rule of thumb that a function returning an error must
not change the state of the caller, assign MISC_DYNAMIC_MINOR back.
The problem is met in a sutuation, when subsys_initcall(misc_init) is
not yet called and misc_class is not created, but misc_register()
modifies statically defined ".minor = MISC_DYNAMIC_MINOR", therefore
implicitly changing the client's logic on next attempt (e.g. retrying
from deferred list) to register a misc device, whose minor number is
converted from dynamic to some unknown static one.
Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/char/misc.c')
| -rw-r--r-- | drivers/char/misc.c | 13 |
1 files changed, 9 insertions, 4 deletions
diff --git a/drivers/char/misc.c b/drivers/char/misc.c index a4d3674e3277..fdb0f9b3fe45 100644 --- a/drivers/char/misc.c +++ b/drivers/char/misc.c @@ -186,12 +186,13 @@ int misc_register(struct miscdevice * misc) { dev_t dev; int err = 0; + bool is_dynamic = (misc->minor == MISC_DYNAMIC_MINOR); INIT_LIST_HEAD(&misc->list); mutex_lock(&misc_mtx); - if (misc->minor == MISC_DYNAMIC_MINOR) { + if (is_dynamic) { int i = find_first_zero_bit(misc_minors, DYNAMIC_MINORS); if (i >= DYNAMIC_MINORS) { err = -EBUSY; @@ -216,9 +217,13 @@ int misc_register(struct miscdevice * misc) device_create_with_groups(misc_class, misc->parent, dev, misc, misc->groups, "%s", misc->name); if (IS_ERR(misc->this_device)) { - int i = DYNAMIC_MINORS - misc->minor - 1; - if (i < DYNAMIC_MINORS && i >= 0) - clear_bit(i, misc_minors); + if (is_dynamic) { + int i = DYNAMIC_MINORS - misc->minor - 1; + + if (i < DYNAMIC_MINORS && i >= 0) + clear_bit(i, misc_minors); + misc->minor = MISC_DYNAMIC_MINOR; + } err = PTR_ERR(misc->this_device); goto out; } |