glib2/SOURCES/2435.patch
2022-03-01 12:36:03 +00:00

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From a879d08e912a4421786b44af479f94f7b4503f5a Mon Sep 17 00:00:00 2001
From: Philip Withnall <pwithnall@endlessos.org>
Date: Mon, 17 Jan 2022 15:27:24 +0000
Subject: [PATCH] gspawn: Report errors with closing file descriptors between
fork/exec
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
If a seccomp policy is set up incorrectly so that it returns `EPERM` for
`close_range()` rather than `ENOSYS` due to it not being recognised, no
error would previously be reported from GLib, but some file descriptors
wouldnt be closed, and that would cause a hung zombie process. The
zombie process would be waiting for one half of a socket to be closed.
Fix that by correctly propagating errors from `close_range()` back to the
parent process so they can be reported correctly.
Distributions which arent yet carrying the Docker fix to correctly
return `ENOSYS` from unrecognised syscalls may want to temporarily carry
an additional patch to fall back to `safe_fdwalk()` if `close_range()`
fails with `EPERM`. This change will not be accepted upstream as `EPERM`
is not the right error for `close_range()` to be returning.
Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
Fixes: #2580
---
glib/gspawn.c | 35 ++++++++++++++++++++++++++---------
1 file changed, 26 insertions(+), 9 deletions(-)
diff --git a/glib/gspawn.c b/glib/gspawn.c
index c2fe306dc..9c2f7ba7b 100644
--- a/glib/gspawn.c
+++ b/glib/gspawn.c
@@ -1457,8 +1457,10 @@ safe_fdwalk (int (*cb)(void *data, int fd), void *data)
}
/* This function is called between fork() and exec() and hence must be
- * async-signal-safe (see signal-safety(7)). */
-static void
+ * async-signal-safe (see signal-safety(7)).
+ *
+ * On failure, `-1` will be returned and errno will be set. */
+static int
safe_closefrom (int lowfd)
{
#if defined(__FreeBSD__) || defined(__OpenBSD__)
@@ -1472,6 +1474,7 @@ safe_closefrom (int lowfd)
* should be safe to use.
*/
(void) closefrom (lowfd);
+ return 0;
#elif defined(__DragonFly__)
/* It is unclear whether closefrom function included in DragonFlyBSD libc_r
* is safe to use because it calls a lot of library functions. It is also
@@ -1479,12 +1482,13 @@ safe_closefrom (int lowfd)
* direct system call here ourselves to avoid possible issues.
*/
(void) syscall (SYS_closefrom, lowfd);
+ return 0;
#elif defined(F_CLOSEM)
/* NetBSD and AIX have a special fcntl command which does the same thing as
* closefrom. NetBSD also includes closefrom function, which seems to be a
* simple wrapper of the fcntl command.
*/
- (void) fcntl (lowfd, F_CLOSEM);
+ return fcntl (lowfd, F_CLOSEM);
#else
#if defined(HAVE_CLOSE_RANGE)
@@ -1494,9 +1498,11 @@ safe_closefrom (int lowfd)
*
* Handle ENOSYS in case its supported in libc but not the kernel; if so,
* fall back to safe_fdwalk(). */
- if (close_range (lowfd, G_MAXUINT, 0) != 0 && errno == ENOSYS)
+ int ret = close_range (lowfd, G_MAXUINT, 0);
+ if (ret == 0 || errno != ENOSYS)
+ return ret;
#endif /* HAVE_CLOSE_RANGE */
- (void) safe_fdwalk (close_func, GINT_TO_POINTER (lowfd));
+ return safe_fdwalk (close_func, GINT_TO_POINTER (lowfd));
#endif
}
@@ -1534,7 +1540,8 @@ enum
CHILD_EXEC_FAILED,
CHILD_OPEN_FAILED,
CHILD_DUP2_FAILED,
- CHILD_FORK_FAILED
+ CHILD_FORK_FAILED,
+ CHILD_CLOSE_FAILED,
};
/* This function is called between fork() and exec() and hence must be
@@ -1650,12 +1657,14 @@ do_exec (gint child_err_report_fd,
if (safe_dup2 (child_err_report_fd, 3) < 0)
write_err_and_exit (child_err_report_fd, CHILD_DUP2_FAILED);
set_cloexec (GINT_TO_POINTER (0), 3);
- safe_closefrom (4);
+ if (safe_closefrom (4) < 0)
+ write_err_and_exit (child_err_report_fd, CHILD_CLOSE_FAILED);
child_err_report_fd = 3;
}
else
{
- safe_fdwalk (set_cloexec, GINT_TO_POINTER (3));
+ if (safe_fdwalk (set_cloexec, GINT_TO_POINTER (3)) < 0)
+ write_err_and_exit (child_err_report_fd, CHILD_CLOSE_FAILED);
}
}
else
@@ -2446,7 +2455,15 @@ fork_exec (gboolean intermediate_child,
_("Failed to fork child process (%s)"),
g_strerror (buf[1]));
break;
-
+
+ case CHILD_CLOSE_FAILED:
+ g_set_error (error,
+ G_SPAWN_ERROR,
+ G_SPAWN_ERROR_FAILED,
+ _("Failed to close file descriptor for child process (%s)"),
+ g_strerror (buf[1]));
+ break;
+
default:
g_set_error (error,
G_SPAWN_ERROR,
--
2.34.1