Messages in this thread | | | Date | Tue, 15 Apr 2008 23:09:45 +0200 | From | "Michael Kerrisk" <> | Subject | core_pattern piping strangeness |
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Hi Andi,
In 2.6.19 you added the pipiing syntax (http://lwn.net/Articles/195310/) to core_pattern. Petr pointed out that this is not yet documented in core(5), so I set to testing it.
The change log has the text:
The core dump proces will run with the privileges and in the name space of the process that caused the core dump.
This appears not to be true (as tested on 2.6.25-rc8). Instead the pipe program is run as root. I'm not sure what "in the name space of the process that caused the core dump" means -- I wondered if it might mean that the current working directory of the program would be the same as that of the process that caused the core dump. However that is not so: the current directory for the pipe program is the root directory.
Can you comment? Am I misunderstanding something?
Test program and shell session shown below.
Cheers,
Michael
$ cat core_pattern_test.c /* core_pattern_test.c */
#define _GNU_SOURCE #include <sys/stat.h> #include <fcntl.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h>
#define BUF_SIZE 1024
int main(int argc, char *argv[]) { int fd, tot; ssize_t numRead; char buf[BUF_SIZE]; FILE *fp;
fd = open(argv[1], O_CREAT | O_WRONLY | O_TRUNC, 0666);
fp = fdopen(fd, "a"); fprintf(fp, "PID=%ld\n", (long) getpid()); fprintf(fp, "cwd=%s\n", get_current_dir_name()); fprintf(fp, "UID=%ld; EUID=%ld\n", (long) getuid(), (long) geteuid());
/* Count bytes in standard input */
tot = 0; while ((numRead = read(STDIN_FILENO, buf, BUF_SIZE)) > 0) tot += numRead; fprintf(fp, "Total bytes in core dump: %d\n", tot);
exit(EXIT_SUCCESS); }
$ cc core_pattern_test.c $ su Password: # echo "|$PWD/a.out $PWD/core.log" > /proc/sys/kernel/core_pattern # exit $ sleep 100 & [1] 5637 $ kill -QUIT %1 [1]+ Quit (core dumped) sleep 100 $ cat core.log PID=5638 cwd=/ UID=0; EUID=0 Total bytes in core dump: 282624
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