Messages in this thread | | | Date | Fri, 10 Jun 2022 19:12:02 +0530 | Subject | Re: [PATCH 1/2] char: lp: ensure that index has not exceeded LP_NO | From | Shreenidhi Shedi <> |
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On 10/06/22 6:58 pm, Greg KH wrote: > On Fri, Jun 03, 2022 at 06:30:39PM +0530, Shreenidhi Shedi wrote: >> From: Shreenidhi Shedi <sshedi@vmware.com> >> >> After finishing the loop, index value can be equal to LP_NO and lp_table >> array is of size LP_NO, so this can end up in accessing an out of bound >> address in lp_register function. >> >> Signed-off-by: Shreenidhi Shedi <sshedi@vmware.com> >> --- >> drivers/char/lp.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/char/lp.c b/drivers/char/lp.c >> index 0e22e3b0a..d474d02b6 100644 >> --- a/drivers/char/lp.c >> +++ b/drivers/char/lp.c >> @@ -972,7 +972,7 @@ static void lp_attach(struct parport *port) >> if (port_num[i] == -1) >> break; >> >> - if (!lp_register(i, port)) >> + if (i < LP_NO && !lp_register(i, port)) >> lp_count++; > > How can this ever be needed? Look at the check further up for the check > of lp_count which prevents this from every going too large. > > So how can an address be accessed out of bound here? > > thanks, > > greg k-h
Thanks for the review. Assume lp_count is less than LP_NO now and we enter the for loop and for some reason for loop exits after i reaching the value LP_NO and right after that we call lp_register() with i and I can be equal to LP_NO.
-- Shedi
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