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authorLuke Shumaker <lukeshu@parabola.nu>2017-11-15 20:36:44 +0100
committerChristian Brauner <christian.brauner@ubuntu.com>2017-11-15 20:47:12 +0100
commita09dfc19edcbac3f96d5410529b724db0a583879 (patch)
treebf4b8207f3ae7ae4a53802a67e092857d320b8b8 /sysdeps
parent2fbce9c2031e70b6bd67876accfc34b0ec492878 (diff)
downloadglibc-a09dfc19edcbac3f96d5410529b724db0a583879.tar.gz
linux ttyname{_r}: Don't bail prematurely [BZ #22145]
Commit 15e9a4f378c8607c2ae1aa465436af4321db0e23 introduced logic for ttyname() sending back ENODEV to signal that we can't get a name for the TTY because we inherited it from a different mount namespace. However, just because we inherited it from a different mount namespace and it isn't available at its original path, doesn't mean that its name is unknowable; we can still try to find it by allowing the normal fall back on iterating through devices. An example scenario where this happens is with "/dev/console" in containers. It's a common practice among container managers to allocate a PTY master/slave pair in the host's mount namespace (the slave having a path like "/dev/pty/$X"), bind mount the slave to "/dev/console" in the container's mount namespace, and send the slave FD to a process in the container. Inside of the container, the slave-end isn't available at its original path ("/dev/pts/$X"), since the container mount namespace has a separate devpts instance from the host (that path may or may not exist in the container; if it does exist, it's not the same PTY slave device). Currently ttyname{_r} sees that the file at the original "/dev/pts/$X" path doesn't match the FD passed to it, and fails early and gives up, even though if it kept searching it would find the TTY at "/dev/console". Fix that; don't have the ENODEV path force an early return inhibiting the fall-back search. This change is based on the previous patch that adds use of is_mytty in getttyname and getttyname_r. Without that change, this effectively reverts 15e9a4f, which made us disregard the false similarity of file pointed to by "/proc/self/fd/$Y", because if it doesn't bail prematurely then that file ("/dev/pts/$X") will just come up again anyway in the fall-back search. Reviewed-by: Christian Brauner <christian.brauner@ubuntu.com>
Diffstat (limited to 'sysdeps')
-rw-r--r--sysdeps/unix/sysv/linux/ttyname.c19
-rw-r--r--sysdeps/unix/sysv/linux/ttyname_r.c20
2 files changed, 24 insertions, 15 deletions
diff --git a/sysdeps/unix/sysv/linux/ttyname.c b/sysdeps/unix/sysv/linux/ttyname.c
index 6e97d2d455..f4c955f25b 100644
--- a/sysdeps/unix/sysv/linux/ttyname.c
+++ b/sysdeps/unix/sysv/linux/ttyname.c
@@ -115,6 +115,7 @@ ttyname (int fd)
char procname[30];
struct stat64 st, st1;
int dostat = 0;
+ int doispty = 0;
char *name;
int save = errno;
struct termios term;
@@ -165,13 +166,7 @@ ttyname (int fd)
&& is_mytty (&st, &st1))
return ttyname_buf;
- /* If the link doesn't exist, then it points to a device in another
- namespace. */
- if (is_pty (&st))
- {
- __set_errno (ENODEV);
- return NULL;
- }
+ doispty = 1;
}
if (__xstat64 (_STAT_VER, "/dev/pts", &st1) == 0 && S_ISDIR (st1.st_mode))
@@ -195,5 +190,15 @@ ttyname (int fd)
name = getttyname ("/dev", &st, save, &dostat);
}
+ if (!name && doispty && is_pty (&st))
+ {
+ /* We failed to figure out the TTY's name, but we can at least
+ signal that we did verify that it really is a PTY slave.
+ This happens when we have inherited the file descriptor from
+ a different mount namespace. */
+ __set_errno (ENODEV);
+ return NULL;
+ }
+
return name;
}
diff --git a/sysdeps/unix/sysv/linux/ttyname_r.c b/sysdeps/unix/sysv/linux/ttyname_r.c
index 58eb919c3f..00eefc2c5c 100644
--- a/sysdeps/unix/sysv/linux/ttyname_r.c
+++ b/sysdeps/unix/sysv/linux/ttyname_r.c
@@ -95,6 +95,7 @@ __ttyname_r (int fd, char *buf, size_t buflen)
char procname[30];
struct stat64 st, st1;
int dostat = 0;
+ int doispty = 0;
int save = errno;
/* Test for the absolute minimal size. This makes life easier inside
@@ -149,14 +150,7 @@ __ttyname_r (int fd, char *buf, size_t buflen)
&& is_mytty (&st, &st1))
return 0;
- /* If the link doesn't exist, then it points to a device in another
- * namespace.
- */
- if (is_pty (&st))
- {
- __set_errno (ENODEV);
- return ENODEV;
- }
+ doispty = 1;
}
/* Prepare the result buffer. */
@@ -190,6 +184,16 @@ __ttyname_r (int fd, char *buf, size_t buflen)
save, &dostat);
}
+ if (ret && doispty && is_pty (&st))
+ {
+ /* We failed to figure out the TTY's name, but we can at least
+ signal that we did verify that it really is a PTY slave.
+ This happens when we have inherited the file descriptor from
+ a different mount namespace. */
+ __set_errno (ENODEV);
+ return ENODEV;
+ }
+
return ret;
}