Bug 108149

Description of problem:

Accroding to the man page for fcntl, a record lock created through a fcntl call
should be preserved across an execve call. This is the case under Red Hat Linue
9 kernel-2.4.20-8smp release, but fails to work under kernel-2.4.20-20.9 release.

Here is a description of our test scenario: A process forks after starting up.
In the child process, it creates an exclusive file lock through fcntl() and then
calls execve(). In the parent process, it tests whether an exclusive lock is
placed on the file. Under kernel-2.4.20-20.9 release, the parent process finds
no lock, whereas under kernel-2.4.20-8smp, the parent process finds that an
exclusive lock is placed on the file.

The source code for our test case includes two files:
/*---First file is named "fcntl_test.cxx", here is the code:---*/

#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>


int main(int argc, char *argv[])
{
   int pid, i;
   FILE *fp;
   struct flock lck;

   /* --- Open a file for writing. */
   printf("fcntl_test: About to open file '/tmp/test.txt' for writing... ");
   fp = fopen("/tmp/test.txt", "w");
   if (fp == NULL) {
      printf("Failed\n");
      exit(1);
   } else {
      printf("Succeeded\n");
   }

   /* --- Now fork. */
   printf("fcntl_test: About to fork...\n");
   pid = fork();

   if (pid == 0) {

      /* --- In child process: Try to place an exclusive lock. */
      printf("fcntl_test Child: Try to place an exclusive lock... ");
      lck.l_type = F_WRLCK;
      lck.l_start = 0;
      lck.l_whence = SEEK_END;
      lck.l_len = 0;
      if (fcntl(fileno(fp), F_SETLK, &lck) < 0) {
         printf("Failed\n");
         exit(2);
      } else {
         printf("Succeeded\n");
      }

      /* --- Try to exec */
      printf("fcntl_test Child: Try to exec fcntl_lock...\n");
      if (execve("fcntl_lock", argv, argv) == -1) {
         printf("fcntl_test Child: execvp Failed\n");
      }
   } else if (pid > 0) {

      /* --- Try to sleep for 5 seconds. */
      printf("fcntl_test Parent: Try to sleep for 5 seconds.\n");
      sleep(5);

      /* --- In parent process: Try to test whether an exclusive lock is */
      /* --- placed on file. Try this for 30 times. */
      printf("fcntl_test Parent: Try 30 times to test whether exclusive lock
exists...\n");
      for (i = 0; i < 30; i++) {
         lck.l_type = F_WRLCK;
         lck.l_start = 0;
         lck.l_whence = SEEK_SET;
         lck.l_len = 0;
         lck.l_pid = (pid_t)0;
         if (fcntl(fileno(fp), F_GETLK, &lck) < 0) {
            printf("   Failed\n");
            exit(3);
         } else {
            if (lck.l_type == F_UNLCK) {
               printf("   No lock placed on file\n");
            } else if (lck.l_type == F_WRLCK) {
               printf("   An exclusive lock placed on file by process %d\n",
                      lck.l_pid);
            } else if (lck.l_type == F_RDLCK) {
               printf("   A shared lock placed on file by process %d\n",
                      lck.l_pid);
            }
         }
      }

      printf("fcntl_test Parent: Now exit\n");
      exit(0);
   } else {
      printf("fcntl_test: fork() failed\n");
      exit(1);
   }
}


/*---Second file is named "fcntl_lock.cxx", here is the code:---*/

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>


int main(int argc, char *argv[])
{
   /* --- Sleep for 10 seconds. */
   printf("fcntl_lock: Now sleep for 10 seconds... \n");
   sleep(10);

   printf("fcntl_lock: Now exit\n");
   exit(0);
}



Version-Release number of selected component (if applicable):

kernel-2.4.20-20.9


How reproducible:

Everytime


Steps to Reproduce:

1.Compile the source code:
gcc fcntl_test.cxx -o fcntl_test
gcc fcntl_lock.cxx -o fcntl_lock

2. Make sure that you have write permission to the /tmp directory and the
directory does NOT contain a file named "test.txt".

3. Copy the executables fcntl_test and fcntl_lock into the same directory (such
as your home directory). cd into this directory and execute:
./fcntl_test


    
Actual results:

The results under kernel-2.4.20-20.9 release:

fcntl_test: About to open file '/tmp/test.txt' for writing... Succeeded
fcntl_test: About to fork...
fcntl_test Parent: Try to sleep for 5 seconds.
fcntl_test Parent: Try 30 times to test whether exclusive lock exists...
   No lock placed on file
   No lock placed on file
   No lock placed on file
   No lock placed on file
   No lock placed on file
   No lock placed on file
   No lock placed on file
   No lock placed on file
   No lock placed on file
   No lock placed on file
   No lock placed on file
   No lock placed on file
   No lock placed on file
   No lock placed on file
   No lock placed on file
   No lock placed on file
   No lock placed on file
   No lock placed on file
   No lock placed on file
   No lock placed on file
   No lock placed on file
   No lock placed on file
   No lock placed on file
   No lock placed on file
   No lock placed on file
   No lock placed on file
   No lock placed on file
   No lock placed on file
   No lock placed on file
   No lock placed on file
fcntl_test Parent: Now exit
fcntl_lock: Now sleep for 10 seconds...
fcntl_lock: Now exit


Expected results:

The results under kernel-2.4.20-8smp release:

fcntl_test: About to open file '/tmp/test.txt' for writing... Succeeded
fcntl_test: About to fork...
fcntl_test Parent: Try to sleep for 5 seconds.
fcntl_test Parent: Try 30 times to test whether exclusive lock exists...
   An exclusive lock placed on file by process 8626
   An exclusive lock placed on file by process 8626
   An exclusive lock placed on file by process 8626
   An exclusive lock placed on file by process 8626
   An exclusive lock placed on file by process 8626
   An exclusive lock placed on file by process 8626
   An exclusive lock placed on file by process 8626
   An exclusive lock placed on file by process 8626
   An exclusive lock placed on file by process 8626
   An exclusive lock placed on file by process 8626
   An exclusive lock placed on file by process 8626
   An exclusive lock placed on file by process 8626
   An exclusive lock placed on file by process 8626
   An exclusive lock placed on file by process 8626
   An exclusive lock placed on file by process 8626
   An exclusive lock placed on file by process 8626
   An exclusive lock placed on file by process 8626
   An exclusive lock placed on file by process 8626
   An exclusive lock placed on file by process 8626
   An exclusive lock placed on file by process 8626
   An exclusive lock placed on file by process 8626
   An exclusive lock placed on file by process 8626
   An exclusive lock placed on file by process 8626
   An exclusive lock placed on file by process 8626
   An exclusive lock placed on file by process 8626
   An exclusive lock placed on file by process 8626
   An exclusive lock placed on file by process 8626
   An exclusive lock placed on file by process 8626
   An exclusive lock placed on file by process 8626
   An exclusive lock placed on file by process 8626
fcntl_test Parent: Now exit
fcntl_lock: Now sleep for 10 seconds...
fcntl_lock: Now exit

Additional info: