From 053fe273434056f551ed8f81daf750db9dab5931 Mon Sep 17 00:00:00 2001 From: Adhemerval Zanella Date: Wed, 23 Mar 2022 17:40:01 -0300 Subject: [PATCH] linux: Fix __closefrom_fallback iterates until max int (BZ#28993) The __closefrom_fallback tries to get a available file descriptor if the initial open ("/proc/self/fd/", ...) fails. It assumes the failure would be only if procfs is not mount (ENOENT), however if the the proc file is not accessible (due some other kernel filtering such apparmor) it will iterate over a potentially large file set issuing close calls. It should only try the close fallback if open returns EMFILE, ENFILE, or ENOMEM. Checked on x86_64-linux-gnu. --- sysdeps/unix/sysv/linux/closefrom_fallback.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/sysdeps/unix/sysv/linux/closefrom_fallback.c b/sysdeps/unix/sysv/linux/closefrom_fallback.c index 60101aa..a9dd0c4 100644 --- a/sysdeps/unix/sysv/linux/closefrom_fallback.c +++ b/sysdeps/unix/sysv/linux/closefrom_fallback.c @@ -30,16 +30,16 @@ _Bool __closefrom_fallback (int from, _Bool dirfd_fallback) { - bool ret = false; - int dirfd = __open_nocancel (FD_TO_FILENAME_PREFIX, O_RDONLY | O_DIRECTORY, 0); if (dirfd == -1) { - /* The closefrom should work even when process can't open new files. */ - if (errno == ENOENT || !dirfd_fallback) - goto err; + /* Return if procfs can not be opened for some reason. */ + if ((errno != EMFILE && errno != ENFILE && errno != ENOMEM) + || !dirfd_fallback) + return false; + /* The closefrom should work even when process can't open new files. */ for (int i = from; i < INT_MAX; i++) { int r = __close_nocancel (i); @@ -54,6 +54,7 @@ __closefrom_fallback (int from, _Bool dirfd_fallback) } char buffer[1024]; + bool ret = false; while (true) { ssize_t ret = __getdents64 (dirfd, buffer, sizeof (buffer)); -- 1.8.3.1