From e79b543156aec759542ca7aa01d727aea548f833 Mon Sep 17 00:00:00 2001
From: Jakub Filak <jfilak@redhat.com>
Date: Wed, 20 May 2015 06:07:15 +0200
Subject: [PATCH] ccpp: do not unlink failed and big user cores

* We might end up deleting an already existing file.
* Kernel does not delete nor truncate core files. Admittedly, kernel
  knows how process's memory is structured, dumps it per logical
  segments and checks whether a next segment can be written.
* 'ulimit -c' does not seem to be a hard limit. Kernel wrote 8192 bytes
  despite $(ulimit -c) == 6.

Related: #1212818

Signed-off-by: Jakub Filak <jfilak@redhat.com>
---
 src/hooks/abrt-hook-ccpp.c | 45 +++++++++++++++++----------------------------
 1 file changed, 17 insertions(+), 28 deletions(-)

diff --git a/src/hooks/abrt-hook-ccpp.c b/src/hooks/abrt-hook-ccpp.c
index 0448216..59fcfce 100644
--- a/src/hooks/abrt-hook-ccpp.c
+++ b/src/hooks/abrt-hook-ccpp.c
@@ -117,8 +117,8 @@ static off_t copyfd_sparse(int src_fd, int dst_fd1, int dst_fd2, off_t size2)
 		size2 -= rd;
 		if (size2 < 0)
 			dst_fd2 = -1;
-//TODO: truncate to 0 or even delete the second file
-//(currently we delete the file later)
+// truncate to 0 or even delete the second file?
+// No, kernel does not delete nor truncate core files.
 	}
  out:
 
@@ -377,13 +377,20 @@ static int open_user_core(uid_t uid, uid_t fsuid, gid_t fsgid, pid_t pid, char *
 
 user_core_fail:
     if (user_core_fd >= 0)
-    {
         close(user_core_fd);
-        unlinkat(dirfd(proc_cwd), core_basename, /*unlink file*/0);
-    }
     return -1;
 }
 
+static int close_user_core(int user_core_fd, off_t core_size)
+{
+    if (user_core_fd >= 0 && (fsync(user_core_fd) != 0 || close(user_core_fd) != 0 || core_size < 0))
+    {
+        perror_msg("Error writing '%s' at '%s'", core_basename, user_pwd);
+        return -1;
+    }
+    return 0;
+}
+
 /* Like xopen, but on error, unlocks and deletes dd and user core */
 static int create_or_die(const char *filename, int user_core_fd)
 {
@@ -398,7 +405,7 @@ static int create_or_die(const char *filename, int user_core_fd)
     if (dd)
         dd_delete(dd);
     if (user_core_fd >= 0)
-        unlinkat(dirfd(proc_cwd), core_basename, /*unlink file*/0);
+        close(user_core_fd);
 
     errno = sv_errno;
     perror_msg_and_die("Can't open '%s'", filename);
@@ -431,19 +438,10 @@ static int create_user_core(int user_core_fd, pid_t pid, off_t ulimit_c)
     if (user_core_fd >= 0)
     {
         off_t core_size = copyfd_size(STDIN_FILENO, user_core_fd, ulimit_c, COPYFD_SPARSE);
-        if (fsync(user_core_fd) != 0 || close(user_core_fd) != 0 || core_size < 0)
-        {
-            /* perror first, otherwise unlink may trash errno */
-            perror_msg("Error writing '%s' at '%s'", core_basename, user_pwd);
-            unlinkat(dirfd(proc_cwd), core_basename, /*only files*/0);
-            goto finito;
-        }
-        if (ulimit_c == 0 || core_size > ulimit_c)
-        {
-            unlinkat(dirfd(proc_cwd), core_basename, /*only files*/0);
+        if (close_user_core(user_core_fd, core_size) != 0)
             goto finito;
-        }
-        log_notice("Saved core dump of pid %lu to %s at '%s' (%llu bytes)", (long)pid, core_basename, user_pwd, (long long)core_size);
+
+        log_notice("Saved core dump of pid %lu to '%s' at '%s' (%llu bytes)", (long)pid, core_basename, user_pwd, (long long)core_size);
     }
     err = 0;
 
@@ -822,6 +820,7 @@ int main(int argc, char** argv)
              * ls: cannot access core*: No such file or directory <=== BAD
              */
             core_size = copyfd_sparse(STDIN_FILENO, abrt_core_fd, user_core_fd, ulimit_c);
+            close_user_core(user_core_fd, core_size);
             if (fsync(abrt_core_fd) != 0 || close(abrt_core_fd) != 0 || core_size < 0)
             {
                 unlink(path);
@@ -832,16 +831,6 @@ int main(int argc, char** argv)
 
                 goto cleanup_and_exit;
             }
-            if (user_core_fd >= 0
-                /* error writing user coredump? */
-             && (fsync(user_core_fd) != 0 || close(user_core_fd) != 0
-                /* user coredump is too big? */
-                || (ulimit_c == 0 /* paranoia */ || core_size > ulimit_c)
-                )
-            ) {
-                /* nuke it (silently) */
-                unlinkat(dirfd(proc_cwd), core_basename, /*unlink file*/0);
-            }
         }
         else
         {
-- 
2.1.0