> There ought to be one that returns a pointer to the first character > that isn't converted - but I'm no expert on the full range of these > functions.
I've searched for a function that parses an int from a string and stores a pointer to the end; I can find some function simple_strtoul that matches this criterion, but it's documented as "This function has caveats. Please use kstrtoul instead." ... and kstrtoul does not store a pointer to the end. The documentation of kstrtoul describes simple_strtoul as obsolete as well. Also, there's no simple_strtou16 function. It seems that the standard C function strtoul has the behaviour you describe as well, but this function is not defined in the kernel except for certain specific architectures. > The problem with strdup() is you get the extra (unlikely) failure path. > 128 bytes of stack won't be a problem if the function is (essentially) > a leaf. > Deep stack use is actually likely to be in the bowels of printf()) > inside an obscure error path. The function already makes a call to kcalloc, so the unlikely out-of- memory error path already exists; a second memory allocation just makes it slightly less unlikely. The two new out-of-memory conditions do happen at different points of the function though, making them have different side effects. I could fix this by moving my code. As for this function being a leaf: keep in mind that this function has the potential of calling printk in an obscure error condition (the user- provided parameter being longer that 128 characters); quirks_param_set calls param_set_copystring, which on its turn calls pr_err, which is a macro for printk. Meanwhile, here's a patch for copying the parameter to the stack: --- drivers/usb/core/quirks.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/drivers/usb/core/quirks.c b/drivers/usb/core/quirks.c index e0b77674869c..86b1a6739b4e 100644 --- a/drivers/usb/core/quirks.c +++ b/drivers/usb/core/quirks.c @@ -12,6 +12,8 @@ #include <linux/usb/hcd.h> #include "usb.h" +#define QUIRKS_PARAM_SIZE 128 + struct quirk_entry { u16 vid; u16 pid; @@ -23,19 +25,21 @@ static DEFINE_MUTEX(quirk_mutex); static struct quirk_entry *quirk_list; static unsigned int quirk_count; -static char quirks_param[128]; +static char quirks_param[QUIRKS_PARAM_SIZE]; -static int quirks_param_set(const char *val, const struct kernel_param *kp) +static int quirks_param_set(const char *value, const struct kernel_param *kp) { + char val[QUIRKS_PARAM_SIZE]; char *p, *field; u16 vid, pid; u32 flags; size_t i; int err; - err = param_set_copystring(val, kp); + err = param_set_copystring(value, kp); if (err) return err; + strscpy(val, value, sizeof(val)); mutex_lock(&quirk_mutex); -- 2.27.0