glebfm/strace
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

If stdin/stdout aren't open on startup, open them to /dev/null

Browse Source 
Otherwise, -oLOGFILE may end up using one of them. This conflicts
with the previous change, which closes stdin/out in strace.

* strace.c (init): If fcntl(F_GETFD) fails on stdin or stdout,
sanitize them: open /dev/null and dup it until fds 0,1,2
are all used up.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
This commit is contained in:
Denys Vlasenko 2016-02-08 18:08:46 +01:00
parent c9f85b3876
commit 0736d4e1a3
1 changed files with 30 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

33
strace.c
View File

@ -1184,6 +1184,16 @@ exec_or_die(void)
perror_msg_and_die("exec");
}
static int open_dev_null(void)
{
int fd = open("/dev/null", O_RDWR);
if (fd < 0) /* /dev not populated? Give me _something_... */
fd = open("/", O_RDWR);
if (fd < 0) /* shouldn't happen... */
perror_msg_and_die("Can't open '/'");
return fd;
}
static void
startup_child(char **argv)
{
@ -1365,9 +1375,7 @@ startup_child(char **argv)
* will reuse them, unexpectedly making a newly opened object "stdin").
*/
close(0);
if (open("/dev/null", O_RDWR) != 0) /* /dev not populated? */
if (open("/", O_RDONLY) != 0) /* shouldn't happen... */
perror_msg_and_die("Can't open '/'");
open_dev_null(); /* opens to fd#0 */
dup2(0, 1);
#if 0
/* A good idea too, but we sometimes need to print error messages */
@ -1715,6 +1723,25 @@ init(int argc, char *argv[])
error_msg("ptrace_setoptions = %#x", ptrace_setoptions);
test_ptrace_seize();
if (fcntl(0, F_GETFD) == -1 || fcntl(1, F_GETFD) == -1) {
/*
* Something weird with our stdin and/or stdout -
* for example, may be not open? In this case,
* ensure that none of the future opens uses them.
*
* This was seen in the wild when /proc/sys/kernel/core_pattern
* was set to "|/bin/strace -o/tmp/LOG PROG":
* kernel runs coredump helper with fd#0 open but fd#1 closed (!),
* therefore LOG gets opened to fd#1, and fd#1 is closed by
* "don't hold up stdin/out open" code soon after.
*/
int fd = open_dev_null();
while (fd >= 0 && fd < 2)
fd = dup(fd);
if (fd > 2)
close(fd);
}
/* Check if they want to redirect the output. */
if (outfname) {
/* See if they want to pipe the output. */