vipw: improve child error handling #1504
Merged
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Always set SIGCHLD handler to default, even if the caller of vipw has
set SIGCHLD to ignore. If SIGCHLD is ignored no zombie processes would
be created, which in turn could mean that kill is called with an already
recycled pid.
Also improved error message if child process fails.
Proof of Concept:
--
#include <signal.h>
#include <unistd.h>
int main(void) {
char *argv[] = { "vipw", NULL };
signal(SIGCHLD, SIG_IGN);
execvp("vipw", argv);
return 1;
}
--
kill -STOP childpid
kill -9 childpid
fg
You will get an improperly formatted warning message. Also the wake up
kill call sent SIGCONT to "childpid" which could have been assigned
to another process already.
This is definitely not a vulnerability. It would take super user
operations, at which point an attacker would have already elevated
permissions.
Signed-off-by: Tobias Stoeckmann tobias@stoeckmann.org