Re: [Crash-utility] [PATCH] Fix segmentation fault when read_string() fails

On Tue, Oct 25, 2022 at 8:00 PM <crash-utility-request(a)redhat.com&gt; wrote: > Date: Tue, 25 Oct 2022 05:48:25 +0000 > From: HAGIO KAZUHITO(?????) <k-hagio-ab(a)nec.com&gt; > To: "Discussion list for crash utility usage, maintenance and > development" <crash-utility(a)redhat.com&gt;, Matias Ezequiel Vara Larsen > <matiasevara(a)gmail.com&gt; > Subject: Re: [Crash-utility] [PATCH] Fix segmentation fault when > read_string() fails > Message-ID: <a1a0ccda-4971-e7f6-a50f-492279ff4cbd(a)nec.com&gt; > Content-Type: text/plain; charset="utf-8" > > On 2022/10/24 18:35, Matias Ezequiel Vara Larsen wrote: >> When read_string() fails, error() dereferences the name variable to print the >> nullchar that the variable points to. However, name points to a nullchar that >> is not in crash's memory-space thus triggering a segmentation fault. This >> commit replaces %s in the error message with %p so the address is printed >> instead. > > Thanks for the report and patch. > > I think that 'nullchar' means null-terminated string and it's a bit > confusing, so I will replace it with 'string'. > >> >> Signed-off-by: Matias Ezequiel Vara Larsen <matias.vara(a)vates.fr&gt; >> --- >> memory.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/memory.c b/memory.c >> index c80ef61..8a1c055 100644 >> --- a/memory.c >> +++ b/memory.c >> @@ -6599,7 +6599,7 @@ page_flags_init_from_pageflag_names(void) >> } >> >> if (!read_string((ulong)name, namebuf, BUFSIZE-1)) { >> - error(INFO, "failed to read pageflag_names entry (i: %d name: \"%s\" mask: %ld)\n", >> + error(INFO, "failed to read pageflag_names entry (i: %d name: \"%p\" mask: %ld)\n", > > I will replace \"%p\" with %lx according to crash's convention. > > With the changes above, > > Acked-by: Kazuhito Hagio <k-hagio-ab(a)nec.com&gt; > > I can fix them when merging in this case, you don't need to resend. > Please wait for another ack. > This change looks good. So: Ack.