linux ttyname and ttyname_r: return link if appropriate
Commit Message
Quoting Mike Frysinger (vapier@gentoo.org):
> On 05 Aug 2016 21:08, Serge E. Hallyn wrote:
> > #ifdef _STATBUF_ST_RDEV
> > && S_ISCHR (st1.st_mode)
> > && st1.st_rdev == st.st_rdev
> > + && st1.st_dev == st.st_dev
> > + && st1.st_ino == st.st_ino
> > #else
> > && st1.st_ino == st.st_ino
> > && st1.st_dev == st.st_dev
> > #endif
>
> wouldn't it be better to shuffle the ifdef then ?
> #ifdef _STATBUF_ST_RDEV
> && S_ISCHR (st1.st_mode)
> && st1.st_rdev == st.st_rdev
> #endif
> && st1.st_ino == st.st_ino
> && st1.st_dev == st.st_dev)
That occurred to me when I looked at it again after sending,
seems reasonable.
Subject: [PATCH] linux ttyname and ttyname_r: return link if appropriate
The current ttyname does the wrong thing in two cases:
1. If the passed-in link (say /proc/self/fd/0) points to a
device, say /dev/pts/2, in a parent mount namespace, and a
/dev/pts/2 exists (in a different devpts) in the current
namespace, then it returns /dev/pts/2. But /dev/pts/2 is
NOT the current tty, it is a different file and device.
2. If the passed-in link (say /proc/self/fd/0) points to
a device, say /dev/pts/2, in a parent mount namespace, and
/dev/pts/2 does not exist in the current namespace, it
returns success but an empty name. As far as I can tell,
there is no reason for it to not return /proc/self/fd/0.
http://pubs.opengroup.org/onlinepubs/009695399/functions/ttyname.html
does not say anything about not returning a link.
---
sysdeps/unix/sysv/linux/ttyname.c | 25 ++++++++++++++++++++++---
sysdeps/unix/sysv/linux/ttyname_r.c | 26 ++++++++++++++++++++++++--
2 files changed, 46 insertions(+), 5 deletions(-)
Comments
Quoting Serge E. Hallyn (serge@hallyn.com):
> Quoting Mike Frysinger (vapier@gentoo.org):
> > On 05 Aug 2016 21:08, Serge E. Hallyn wrote:
> > > #ifdef _STATBUF_ST_RDEV
> > > && S_ISCHR (st1.st_mode)
> > > && st1.st_rdev == st.st_rdev
> > > + && st1.st_dev == st.st_dev
> > > + && st1.st_ino == st.st_ino
> > > #else
> > > && st1.st_ino == st.st_ino
> > > && st1.st_dev == st.st_dev
> > > #endif
> >
> > wouldn't it be better to shuffle the ifdef then ?
> > #ifdef _STATBUF_ST_RDEV
> > && S_ISCHR (st1.st_mode)
> > && st1.st_rdev == st.st_rdev
> > #endif
> > && st1.st_ino == st.st_ino
> > && st1.st_dev == st.st_dev)
>
> That occurred to me when I looked at it again after sending,
> seems reasonable.
Is this now ready to be applied? More peopel appear to be running into
it, https://github.com/lxc/lxc/issues/554
> Subject: [PATCH] linux ttyname and ttyname_r: return link if appropriate
>
> The current ttyname does the wrong thing in two cases:
>
> 1. If the passed-in link (say /proc/self/fd/0) points to a
> device, say /dev/pts/2, in a parent mount namespace, and a
> /dev/pts/2 exists (in a different devpts) in the current
> namespace, then it returns /dev/pts/2. But /dev/pts/2 is
> NOT the current tty, it is a different file and device.
>
> 2. If the passed-in link (say /proc/self/fd/0) points to
> a device, say /dev/pts/2, in a parent mount namespace, and
> /dev/pts/2 does not exist in the current namespace, it
> returns success but an empty name. As far as I can tell,
> there is no reason for it to not return /proc/self/fd/0.
> http://pubs.opengroup.org/onlinepubs/009695399/functions/ttyname.html
> does not say anything about not returning a link.
> ---
> sysdeps/unix/sysv/linux/ttyname.c | 25 ++++++++++++++++++++++---
> sysdeps/unix/sysv/linux/ttyname_r.c | 26 ++++++++++++++++++++++++--
> 2 files changed, 46 insertions(+), 5 deletions(-)
>
> diff --git a/sysdeps/unix/sysv/linux/ttyname.c b/sysdeps/unix/sysv/linux/ttyname.c
> index 7a001b4..3065ed4 100644
> --- a/sysdeps/unix/sysv/linux/ttyname.c
> +++ b/sysdeps/unix/sysv/linux/ttyname.c
> @@ -25,6 +25,7 @@
> #include <unistd.h>
> #include <string.h>
> #include <stdlib.h>
> +#include <sys/sysmacros.h>
>
> #include <_itoa.h>
>
> @@ -33,6 +34,19 @@
> char *__ttyname;
> #endif
>
> +/* Return true if this is a UNIX98 pty device, as defined in
> + linux/Documentation/devices.txt. */
> +static int
> +is_pty (struct stat64 *sb)
> +{
> +#ifdef _STATBUF_ST_RDEV
> + int m = major (sb->st_rdev);
> + return (136 <= m && m <= 143);
> +#else
> + return false;
> +#endif
> +}
> +
> static char *getttyname (const char *dev, dev_t mydev,
> ino64_t myino, int save, int *dostat)
> internal_function;
> @@ -170,12 +184,17 @@ ttyname (int fd)
> #ifdef _STATBUF_ST_RDEV
> && S_ISCHR (st1.st_mode)
> && st1.st_rdev == st.st_rdev
> -#else
> - && st1.st_ino == st.st_ino
> - && st1.st_dev == st.st_dev
> #endif
> + && st1.st_dev == st.st_dev
> + && st1.st_ino == st.st_ino
> )
> return ttyname_buf;
> +
> + /* If the link doesn't exist, then it points to a device in another
> + namespace. If it is a UNIX98 pty, then return the /proc/self
> + fd, as it points to a name unreachable in our namespace. */
> + if (is_pty (&st) && strlen (procname) < buflen - 1)
> + return strcpy (ttyname_buf, procname);
> }
>
> if (__xstat64 (_STAT_VER, "/dev/pts", &st1) == 0 && S_ISDIR (st1.st_mode))
> diff --git a/sysdeps/unix/sysv/linux/ttyname_r.c b/sysdeps/unix/sysv/linux/ttyname_r.c
> index d15bc74..97527c0 100644
> --- a/sysdeps/unix/sysv/linux/ttyname_r.c
> +++ b/sysdeps/unix/sysv/linux/ttyname_r.c
> @@ -25,6 +25,7 @@
> #include <unistd.h>
> #include <string.h>
> #include <stdlib.h>
> +#include <sys/sysmacros.h>
>
> #include <_itoa.h>
>
> @@ -32,6 +33,19 @@ static int getttyname_r (char *buf, size_t buflen,
> dev_t mydev, ino64_t myino, int save,
> int *dostat) internal_function;
>
> +/* Return true if this is a UNIX98 pty device, as defined in
> + linux/Documentation/devices.txt. */
> +static int
> +is_pty (struct stat64 *sb)
> +{
> +#ifdef _STATBUF_ST_RDEV
> + int m = major (sb->st_rdev);
> + return (136 <= m && m <= 143);
> +#else
> + return false;
> +#endif
> +}
> +
> static int
> internal_function attribute_compat_text_section
> getttyname_r (char *buf, size_t buflen, dev_t mydev, ino64_t myino,
> @@ -152,12 +166,20 @@ __ttyname_r (int fd, char *buf, size_t buflen)
> #ifdef _STATBUF_ST_RDEV
> && S_ISCHR (st1.st_mode)
> && st1.st_rdev == st.st_rdev
> -#else
> +#endif
> && st1.st_ino == st.st_ino
> && st1.st_dev == st.st_dev
> -#endif
> )
> return 0;
> +
> + /* If the link doesn't exist, then it points to a device in another
> + namespace. If it is a UNIX98 pty, then return the /proc/self
> + fd, as it points to a name unreachable in our namespace. */
> + if (is_pty (&st) && strlen (procname) < buflen - 1)
> + {
> + strcpy (buf, procname);
> + return 0;
> + }
> }
>
> /* Prepare the result buffer. */
> --
> 2.7.4
On Sat, Aug 06, 2016 at 10:00:02AM -0500, Serge E. Hallyn wrote:
[...]
> Subject: [PATCH] linux ttyname and ttyname_r: return link if appropriate
Please compare
> @@ -170,12 +184,17 @@ ttyname (int fd)
> #ifdef _STATBUF_ST_RDEV
> && S_ISCHR (st1.st_mode)
> && st1.st_rdev == st.st_rdev
> -#else
> - && st1.st_ino == st.st_ino
> - && st1.st_dev == st.st_dev
> #endif
> + && st1.st_dev == st.st_dev
> + && st1.st_ino == st.st_ino
with
> @@ -152,12 +166,20 @@ __ttyname_r (int fd, char *buf, size_t buflen)
> #ifdef _STATBUF_ST_RDEV
> && S_ISCHR (st1.st_mode)
> && st1.st_rdev == st.st_rdev
> -#else
> +#endif
> && st1.st_ino == st.st_ino
> && st1.st_dev == st.st_dev
> -#endif
Wouldn't it be better if both functions implemented these comparisons
exactly the same way?
@@ -25,6 +25,7 @@
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
+#include <sys/sysmacros.h>
#include <_itoa.h>
@@ -33,6 +34,19 @@
char *__ttyname;
#endif
+/* Return true if this is a UNIX98 pty device, as defined in
+ linux/Documentation/devices.txt. */
+static int
+is_pty (struct stat64 *sb)
+{
+#ifdef _STATBUF_ST_RDEV
+ int m = major (sb->st_rdev);
+ return (136 <= m && m <= 143);
+#else
+ return false;
+#endif
+}
+
static char *getttyname (const char *dev, dev_t mydev,
ino64_t myino, int save, int *dostat)
internal_function;
@@ -170,12 +184,17 @@ ttyname (int fd)
#ifdef _STATBUF_ST_RDEV
&& S_ISCHR (st1.st_mode)
&& st1.st_rdev == st.st_rdev
-#else
- && st1.st_ino == st.st_ino
- && st1.st_dev == st.st_dev
#endif
+ && st1.st_dev == st.st_dev
+ && st1.st_ino == st.st_ino
)
return ttyname_buf;
+
+ /* If the link doesn't exist, then it points to a device in another
+ namespace. If it is a UNIX98 pty, then return the /proc/self
+ fd, as it points to a name unreachable in our namespace. */
+ if (is_pty (&st) && strlen (procname) < buflen - 1)
+ return strcpy (ttyname_buf, procname);
}
if (__xstat64 (_STAT_VER, "/dev/pts", &st1) == 0 && S_ISDIR (st1.st_mode))
@@ -25,6 +25,7 @@
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
+#include <sys/sysmacros.h>
#include <_itoa.h>
@@ -32,6 +33,19 @@ static int getttyname_r (char *buf, size_t buflen,
dev_t mydev, ino64_t myino, int save,
int *dostat) internal_function;
+/* Return true if this is a UNIX98 pty device, as defined in
+ linux/Documentation/devices.txt. */
+static int
+is_pty (struct stat64 *sb)
+{
+#ifdef _STATBUF_ST_RDEV
+ int m = major (sb->st_rdev);
+ return (136 <= m && m <= 143);
+#else
+ return false;
+#endif
+}
+
static int
internal_function attribute_compat_text_section
getttyname_r (char *buf, size_t buflen, dev_t mydev, ino64_t myino,
@@ -152,12 +166,20 @@ __ttyname_r (int fd, char *buf, size_t buflen)
#ifdef _STATBUF_ST_RDEV
&& S_ISCHR (st1.st_mode)
&& st1.st_rdev == st.st_rdev
-#else
+#endif
&& st1.st_ino == st.st_ino
&& st1.st_dev == st.st_dev
-#endif
)
return 0;
+
+ /* If the link doesn't exist, then it points to a device in another
+ namespace. If it is a UNIX98 pty, then return the /proc/self
+ fd, as it points to a name unreachable in our namespace. */
+ if (is_pty (&st) && strlen (procname) < buflen - 1)
+ {
+ strcpy (buf, procname);
+ return 0;
+ }
}
/* Prepare the result buffer. */