From bb96fc42956c9ed926a1b958ab715f8b4a663dec Mon Sep 17 00:00:00 2001 From: Craig Small Date: Sun, 5 Jan 2020 15:05:55 +1100 Subject: [PATCH] pgrep: check sanity of SC_ARG_MAX A kernel change means we cannot trust what sysconf(SC_ARG_MAX) returns. We clamp it so its more than 4096 and less than 128*1024 which is what findutils does. References: procps-ng/procps#152 https://git.savannah.gnu.org/cgit/findutils.git/tree/lib/buildcmd.c#n535 https://lwn.net/Articles/727862/ --- pgrep.c | 22 +++++++++++++++++++++- 1 file changed, 21 insertions(+), 1 deletion(-) diff --git a/pgrep.c b/pgrep.c index 01563db..bde7448 100644 --- a/pgrep.c +++ b/pgrep.c @@ -485,6 +485,26 @@ static regex_t * do_regcomp (void) return preg; } +/* + * SC_ARG_MAX used to return the maximum size a command line can be + * however changes to the kernel mean this can be bigger than we can + * alloc. Clamp it to 128kB like xargs and friends do + * Should also not be smaller than POSIX_ARG_MAX which is 4096 + */ +static size_t get_arg_max(void) +{ +#define MIN_ARG_SIZE 4096u +#define MAX_ARG_SIZE (128u * 1024u) + + size_t val = sysconf(_SC_ARG_MAX); + + if (val < MIN_ARG_SIZE) + val = MIN_ARG_SIZE; + if (val > MAX_ARG_SIZE) + val = MAX_ARG_SIZE; + + return val; +} static struct el * select_procs (int *num) { PROCTAB *ptp; @@ -497,7 +517,7 @@ static struct el * select_procs (int *num) regex_t *preg; pid_t myself = getpid(); struct el *list = NULL; - long cmdlen = sysconf(_SC_ARG_MAX) * sizeof(char); + long cmdlen = get_arg_max() * sizeof(char); char *cmdline = xmalloc(cmdlen); char *cmdsearch = xmalloc(cmdlen); char *cmdoutput = xmalloc(cmdlen); -- GitLab