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Blame SOURCES/0096-ccpp-do-not-use-value-of-proc-PID-cwd-for-chdir.patch

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From 806bb07571b698d90169c3b73cb65cd09c900284 Mon Sep 17 00:00:00 2001
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From: Jakub Filak <jfilak@redhat.com>
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Date: Fri, 17 Apr 2015 14:40:20 +0200
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Subject: [ABRT PATCH] ccpp: do not use value of /proc/PID/cwd for chdir
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Avoid symlink resolutions.
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This issue was discovered by Florian Weimer of Red Hat Product Security.
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Signed-off-by: Jakub Filak <jfilak@redhat.com>
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---
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 src/hooks/abrt-hook-ccpp.c | 85 +++++++++++++++++++++++-----------------------
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 1 file changed, 42 insertions(+), 43 deletions(-)
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diff --git a/src/hooks/abrt-hook-ccpp.c b/src/hooks/abrt-hook-ccpp.c
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index 82ff555..d600bb7 100644
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--- a/src/hooks/abrt-hook-ccpp.c
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+++ b/src/hooks/abrt-hook-ccpp.c
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@@ -144,6 +144,7 @@ static off_t copyfd_sparse(int src_fd, int dst_fd1, int dst_fd2, off_t size2)
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 /* Global data */
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 static char *user_pwd;
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+static DIR *proc_cwd;
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 static char *proc_pid_status;
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 static struct dump_dir *dd;
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 static int user_core_fd = -1;
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@@ -163,13 +164,6 @@ static int user_core_fd = -1;
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  */
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 static const char percent_specifiers[] = "%scpugteh";
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 static char *core_basename = (char*) "core";
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-/*
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- * Used for error messages only.
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- * It is either the same as core_basename if it is absolute,
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- * or $PWD/core_basename.
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- */
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-static char *full_core_basename;
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-
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 static char* get_executable(pid_t pid, int *fd_p)
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 {
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@@ -198,6 +192,18 @@ static char* get_executable(pid_t pid, int *fd_p)
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     return executable;
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 }
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+static DIR *open_cwd(pid_t pid)
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+{
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+    char buf[sizeof("/proc/%lu/cwd") + sizeof(long)*3];
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+    sprintf(buf, "/proc/%lu/cwd", (long)pid);
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+
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+    DIR *cwd = opendir(buf);
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+    if (cwd == NULL)
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+        perror_msg("Can't open process's CWD for CompatCore");
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+
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+    return cwd;
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+}
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+
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 static char* get_cwd(pid_t pid)
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 {
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     char buf[sizeof("/proc/%lu/cwd") + sizeof(long)*3];
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@@ -268,13 +274,9 @@ static int dump_suid_policy()
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 static int open_user_core(uid_t uid, uid_t fsuid, pid_t pid, char **percent_values)
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 {
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-    errno = 0;
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-    if (user_pwd == NULL
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-     || chdir(user_pwd) != 0
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-    ) {
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-        perror_msg("Can't cd to '%s'", user_pwd);
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+    proc_cwd = open_cwd(pid);
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+    if (proc_cwd == NULL)
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         return -1;
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-    }
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     struct passwd* pw = getpwuid(uid);
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     gid_t gid = pw ? pw->pw_gid : uid;
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@@ -337,15 +339,10 @@ static int open_user_core(uid_t uid, uid_t fsuid, pid_t pid, char **percent_valu
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         }
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     }
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-    full_core_basename = core_basename;
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-    if (core_basename[0] != '/')
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+    if (g_need_nonrelative && core_basename[0] != '/')
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     {
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-        if (g_need_nonrelative)
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-        {
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-            error_msg("Current suid_dumpable policy prevents from saving core dumps according to relative core_pattern");
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-            return -1;
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-        }
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-        core_basename = concat_path_file(user_pwd, core_basename);
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+        error_msg("Current suid_dumpable policy prevents from saving core dumps according to relative core_pattern");
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+        return -1;
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     }
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     /* Open (create) compat core file.
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@@ -381,7 +378,7 @@ static int open_user_core(uid_t uid, uid_t fsuid, pid_t pid, char **percent_valu
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     struct stat sb;
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     errno = 0;
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     /* Do not O_TRUNC: if later checks fail, we do not want to have file already modified here */
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-    int user_core_fd = open(core_basename, O_WRONLY | O_CREAT | O_NOFOLLOW | g_user_core_flags, 0600); /* kernel makes 0600 too */
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+    int user_core_fd = openat(dirfd(proc_cwd), core_basename, O_WRONLY | O_CREAT | O_NOFOLLOW | g_user_core_flags, 0600); /* kernel makes 0600 too */
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     xsetegid(0);
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     xseteuid(0);
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     if (user_core_fd < 0
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@@ -391,15 +388,15 @@ static int open_user_core(uid_t uid, uid_t fsuid, pid_t pid, char **percent_valu
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      || sb.st_uid != fsuid
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     ) {
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         if (user_core_fd < 0)
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-            perror_msg("Can't open '%s'", full_core_basename);
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+            perror_msg("Can't open '%s' at '%s'", core_basename, user_pwd);
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         else
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-            perror_msg("'%s' is not a regular file with link count 1 owned by UID(%d)", full_core_basename, fsuid);
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+            perror_msg("'%s' at '%s' is not a regular file with link count 1 owned by UID(%d)", core_basename, user_pwd, fsuid);
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         return -1;
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     }
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     if (ftruncate(user_core_fd, 0) != 0) {
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         /* perror first, otherwise unlink may trash errno */
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-        perror_msg("Can't truncate '%s' to size 0", full_core_basename);
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-        unlink(core_basename);
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+        perror_msg("Can't truncate '%s' at '%s' to size 0", core_basename, user_pwd);
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+        unlinkat(dirfd(proc_cwd), core_basename, /*unlink file*/0);
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         return -1;
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     }
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@@ -466,10 +463,8 @@ static int create_or_die(const char *filename)
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     if (dd)
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         dd_delete(dd);
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     if (user_core_fd >= 0)
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-    {
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-        xchdir(user_pwd);
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-        unlink(core_basename);
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-    }
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+        unlinkat(dirfd(proc_cwd), core_basename, /*unlink file*/0);
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+
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     errno = sv_errno;
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     perror_msg_and_die("Can't open '%s'", filename);
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 }
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@@ -573,7 +568,7 @@ int main(int argc, char** argv)
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                         (long)pid, executable);
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     }
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-    user_pwd = get_cwd(pid); /* may be NULL on error */
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+    user_pwd = get_cwd(pid);
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     log_notice("user_pwd:'%s'", user_pwd);
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     sprintf(path, "/proc/%lu/status", (long)pid);
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@@ -672,6 +667,8 @@ int main(int argc, char** argv)
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             error_msg_and_die("Error saving '%s'", path);
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         }
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         log("Saved core dump of pid %lu (%s) to %s (%llu bytes)", (long)pid, executable, path, (long long)core_size);
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+        if (proc_cwd != NULL)
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+            closedir(proc_cwd);
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         return 0;
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     }
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@@ -791,10 +788,7 @@ int main(int argc, char** argv)
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             unlink(path);
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             dd_delete(dd);
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             if (user_core_fd >= 0)
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-            {
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-                xchdir(user_pwd);
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-                unlink(core_basename);
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-            }
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+                unlinkat(dirfd(proc_cwd), core_basename, /*unlink file*/0);
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             /* copyfd_sparse logs the error including errno string,
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              * but it does not log file name */
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             error_msg_and_die("Error writing '%s'", path);
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@@ -807,8 +801,7 @@ int main(int argc, char** argv)
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             )
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         ) {
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             /* nuke it (silently) */
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-            xchdir(user_pwd);
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-            unlink(core_basename);
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+            unlinkat(dirfd(proc_cwd), core_basename, /*unlink file*/0);
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         }
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 /* Because of #1211835 and #1126850 */
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@@ -879,6 +872,8 @@ int main(int argc, char** argv)
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         }
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         free(rootdir);
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+        if (proc_cwd != NULL)
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+            closedir(proc_cwd);
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         return 0;
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     }
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@@ -890,19 +885,23 @@ int main(int argc, char** argv)
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         if (fsync(user_core_fd) != 0 || close(user_core_fd) != 0 || core_size < 0)
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         {
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             /* perror first, otherwise unlink may trash errno */
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-            perror_msg("Error writing '%s'", full_core_basename);
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-            xchdir(user_pwd);
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-            unlink(core_basename);
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+            perror_msg("Error writing '%s' at '%s'", core_basename, user_pwd);
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+            unlinkat(dirfd(proc_cwd), core_basename, /*unlink file*/0);
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+            if (proc_cwd != NULL)
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+                closedir(proc_cwd);
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             return 1;
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         }
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         if (ulimit_c == 0 || core_size > ulimit_c)
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         {
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-            xchdir(user_pwd);
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-            unlink(core_basename);
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+            unlinkat(dirfd(proc_cwd), core_basename, /*unlink file*/0);
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+            if (proc_cwd != NULL)
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+                closedir(proc_cwd);
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             return 1;
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         }
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-        log("Saved core dump of pid %lu to %s (%llu bytes)", (long)pid, full_core_basename, (long long)core_size);
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+        log("Saved core dump of pid %lu to %s at %s (%llu bytes)", (long)pid, core_basename, user_pwd, (long long)core_size);
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     }
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+    if (proc_cwd != NULL)
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+        closedir(proc_cwd);
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     return 0;
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 }
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-- 
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1.8.3.1
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