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authorUlrich Drepper <drepper@redhat.com>2000-09-26 06:42:06 +0000
committerUlrich Drepper <drepper@redhat.com>2000-09-26 06:42:06 +0000
commit3ee561ad4606d73a351d34034789d94c9570026d (patch)
treea1dffa080058a8d81396074eba1e5c87ad42b2c0 /sysdeps/generic/check_fds.c
parent5f2de3379caae38ce49b6db1331105d6bd162316 (diff)
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Update.
* sysdeps/unix/sysv/linux/check_fds.c: New file. * sysdeps/generic/check_fds.c: Check that file opened is really /dev/null.
Diffstat (limited to 'sysdeps/generic/check_fds.c')
-rw-r--r--sysdeps/generic/check_fds.c30
1 files changed, 25 insertions, 5 deletions
diff --git a/sysdeps/generic/check_fds.c b/sysdeps/generic/check_fds.c
index 4eea168794..9891b9c865 100644
--- a/sysdeps/generic/check_fds.c
+++ b/sysdeps/generic/check_fds.c
@@ -20,6 +20,8 @@
#include <fcntl.h>
#include <paths.h>
#include <unistd.h>
+#include <sys/stat.h>
+#include <sys/sysmacros.h>
/* Try to get a machine dependent instruction which will make the
program crash. This is used in case everything else fails. */
@@ -38,11 +40,22 @@ check_one_fd (int fd, int mode)
if (__builtin_expect (__libc_fcntl (fd, F_GETFD), 0) == -1
&& errno == EBADF)
{
+ struct stat64 st;
+
/* Something is wrong with this descriptor, it's probably not
opened. Open /dev/null so that the SUID program we are
about to start does not accidently use this descriptor. */
int nullfd = __libc_open (_PATH_DEVNULL, mode);
- if (__builtin_expect (nullfd, 0) == -1)
+ /* We are very paranoid here. With all means we try to ensure
+ that we are actually opening the /dev/null device and nothing
+ else. */
+ if (__builtin_expect (nullfd, 0) == -1
+ || __builtin_expect (__fxstat64 (_STAT_VER, nullfd, &st), 0) != 0
+ || __builtin_expect (S_ISCHR (st.st_mode), 1) == 0
+#if defined DEV_NULL_MAJOR && defined DEV_NULL_MINOR
+ || st.st_rdev != makedev (DEV_NULL_MAJOR, DEV_NULL_MINOR)
+#endif
+ )
/* We cannot even give an error message here since it would
run into the same problems. */
while (1)
@@ -55,8 +68,15 @@ check_one_fd (int fd, int mode)
void
__libc_check_standard_fds (void)
{
-/* Check all three standard file descriptors. */
- check_one_fd (STDIN_FILENO, O_RDONLY);
- check_one_fd (STDOUT_FILENO, O_RDWR);
- check_one_fd (STDERR_FILENO, O_RDWR);
+ /* This is really paranoid but some people actually are. If /dev/null
+ should happen to be a symlink to somewhere else and not the device
+ commonly known as "/dev/null" be bail out. We can detect this with
+ the O_NOFOLLOW flag for open() but only on some system. */
+#ifndef O_NOFOLLOW
+# define O_NOFOLLOW 0
+#endif
+ /* Check all three standard file descriptors. */
+ check_one_fd (STDIN_FILENO, O_RDONLY | O_NOFOLLOW);
+ check_one_fd (STDOUT_FILENO, O_RDWR | O_NOFOLLOW);
+ check_one_fd (STDERR_FILENO, O_RDWR | O_NOFOLLOW);
}