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Re: [PATCH v2 3/5] linux ttyname and ttyname_r: Make the TTY equivalence tests consistent [BZ #22145]
- From: Christian Brauner <christian dot brauner at ubuntu dot com>
- To: Luke Shumaker <lukeshu at parabola dot nu>
- Cc: libc-alpha at sourceware dot org
- Date: Mon, 6 Nov 2017 14:22:45 +0100
- Subject: Re: [PATCH v2 3/5] linux ttyname and ttyname_r: Make the TTY equivalence tests consistent [BZ #22145]
- Authentication-results: sourceware.org; auth=none
- References: <20171102185346.1386-1-lukeshu@parabola.nu> <20171102185346.1386-4-lukeshu@parabola.nu>
On Thu, Nov 02, 2017 at 02:53:44PM -0400, Luke Shumaker wrote:
> In the ttyname and ttyname_r routines on Linux, at several points it
> it needs to test if a given TTY is the TTY we are looking for. It used to
> be that this test was (to see if `maybe` is `mytty`):
>
> __xstat64(_STAT_VER, maybe_filename, &maybe) == 0
> #ifdef _STATBUF_ST_RDEV
> && S_ISCHR(maybe.st_mode) && maybe.st_rdev == mytty.st_rdev
> #else
> && maybe.st_ino == mytty.st_ino && maybe.st_dev == mytty.st_dev
> #endif
>
> This check appears in several places.
>
> Then, in commit 15e9a4f3 by Christian Brauner
> <christian.brauner@canonical.com>, that check changed to:
>
> __xstat64(_STAT_VER, maybe_filename, &maybe) == 0
> #ifdef _STATBUF_ST_RDEV
> && S_ISCHR(maybe.st_mode) && maybe.st_rdev == mytty.st_rdev
> #endif
> && maybe.st_ino == mytty.st_ino && maybe.st_dev == mytty.st_dev
>
> That is, he made st_ino and st_dev checks happen even if we have the
> st_rdev member. This is a good change, because kernel namespaces allow you
> to create a new namespace, and to create a new device with the same
> st_rdev, but isn't the same file.
>
> However, this check appears twice in each file (ttyname.c and
> ttyname_r.c), but Christian only changed it in one place in each file.
>
> Make it easy to keep consistent by pulling the check in to a static inline
> function, is_mytty.
>
> While we're at it, go ahead and have the existing is_pty return a bool
> (instead of an int) to keep ttyname.h consistent, per
> <https://sourceware.org/ml/libc-alpha/2017-10/msg00532.html>.
>
> The linux tst-ttyname test hasn't been added yet (to avoid breaking
> `git bisect`), but for reference, here's how each relevent change so
> far affects the testcases that will be in it:
>
> | | before | | make tests |
> | | 15e9a4f | 15e9a4f | consistent |
> |---------------------------------+---------+---------+------------|
> | basic smoketest | PASS | PASS | PASS |
> | no conflict, no match | PASS[1] | PASS | PASS |
> | no conflict, console | PASS | FAIL! | FAIL |
> | conflict, no match | FAIL | PASS! | PASS |
> | conflict, console | FAIL | FAIL | FAIL |
> | with readlink target | PASS | PASS | PASS |
> | with readlink trap; fallback | FAIL | FAIL | FAIL |
> | with readlink trap; no fallback | FAIL | PASS! | PASS |
> | with search-path trap | FAIL | FAIL | PASS! |
> |---------------------------------+---------+---------+------------|
> | | 4/9 | 5/9 | 6/9 |
>
> [1]: 15e9a4f introduced a semantic that, under certain failure
> conditions, ttyname sets errno=ENODEV, where previously it
> didn't set errno; it's not quite fair to hold "before 15e9a4f"
> ttyname to those new semantics. This testcase actually fails,
> but would have passed if we tested for the old the semantics.
>
> This only fixed one testcase, but most of the remaining failures
> require both this fix and the subsequent fix in order to pass.
>
> v2:
> - Rearranged commit order
> - Expanded commit message
> - Reformatted is_mytty
> - Made is_pty and is_mytty return bool instead of int
> - Specify 'const' on pointer arguments as necessary
> ---
> ChangeLog | 7 +++++++
> sysdeps/unix/sysv/linux/ttyname.c | 40 ++++++++----------------------------
> sysdeps/unix/sysv/linux/ttyname.h | 14 ++++++++++++-
> sysdeps/unix/sysv/linux/ttyname_r.c | 41 ++++++++-----------------------------
> 4 files changed, 37 insertions(+), 65 deletions(-)
Fyi, I'm going to fix up the commit message in a few places. The code itself
looks fine to me.
Reviewed-By: Christian Brauner <christian.brauner@ubuntu.com>
>
> diff --git a/ChangeLog b/ChangeLog
> index 2c7770fbbb..4c282f8f47 100644
> --- a/ChangeLog
> +++ b/ChangeLog
> @@ -1,5 +1,12 @@
> 2017-11-02 Luke Shumaker <lukeshu@parabola.nu>
>
> + [BZ #22145]
> + * sysdeps/unix/sysv/linux/ttyname.h
> + (is_pty): Change return type from int to bool.
> + (is_mytty): New function.
> + * sysdeps/unix/sysv/linux/ttyname.c: Call is_mytty.
> + * sysdeps/unix/sysv/linux/ttyname_r.c: Likewise.
> +
> * sysdeps/unix/sysv/linux/ttyname.h (is_pty): Update doc reference.
>
> * manual/terminal.texi (Is It a Terminal):
> diff --git a/sysdeps/unix/sysv/linux/ttyname.c b/sysdeps/unix/sysv/linux/ttyname.c
> index 116cf350e5..6e97d2d455 100644
> --- a/sysdeps/unix/sysv/linux/ttyname.c
> +++ b/sysdeps/unix/sysv/linux/ttyname.c
> @@ -35,14 +35,14 @@
> char *__ttyname;
> #endif
>
> -static char *getttyname (const char *dev, dev_t mydev,
> - ino64_t myino, int save, int *dostat);
> +static char *getttyname (const char *dev, const struct stat64 *mytty,
> + int save, int *dostat);
>
> libc_freeres_ptr (static char *getttyname_name);
>
> static char *
> attribute_compat_text_section
> -getttyname (const char *dev, dev_t mydev, ino64_t myino, int save, int *dostat)
> +getttyname (const char *dev, const struct stat64 *mytty, int save, int *dostat)
> {
> static size_t namelen;
> struct stat64 st;
> @@ -63,7 +63,7 @@ getttyname (const char *dev, dev_t mydev, ino64_t myino, int save, int *dostat)
> *((char *) __mempcpy (getttyname_name, dev, devlen - 1)) = '/';
>
> while ((d = __readdir64 (dirstream)) != NULL)
> - if ((d->d_fileno == myino || *dostat)
> + if ((d->d_fileno == mytty->st_ino || *dostat)
> && strcmp (d->d_name, "stdin")
> && strcmp (d->d_name, "stdout")
> && strcmp (d->d_name, "stderr"))
> @@ -85,12 +85,7 @@ getttyname (const char *dev, dev_t mydev, ino64_t myino, int save, int *dostat)
> }
> memcpy (&getttyname_name[devlen], d->d_name, dlen);
> if (__xstat64 (_STAT_VER, getttyname_name, &st) == 0
> -#ifdef _STATBUF_ST_RDEV
> - && S_ISCHR (st.st_mode) && st.st_rdev == mydev
> -#else
> - && d->d_fileno == myino && st.st_dev == mydev
> -#endif
> - )
> + && is_mytty (mytty, &st))
> {
> (void) __closedir (dirstream);
> #if 0
> @@ -167,12 +162,7 @@ ttyname (int fd)
> /* Verify readlink result, fall back on iterating through devices. */
> if (ttyname_buf[0] == '/'
> && __xstat64 (_STAT_VER, ttyname_buf, &st1) == 0
> -#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)
> + && is_mytty (&st, &st1))
> return ttyname_buf;
>
> /* If the link doesn't exist, then it points to a device in another
> @@ -186,11 +176,7 @@ ttyname (int fd)
>
> if (__xstat64 (_STAT_VER, "/dev/pts", &st1) == 0 && S_ISDIR (st1.st_mode))
> {
> -#ifdef _STATBUF_ST_RDEV
> - name = getttyname ("/dev/pts", st.st_rdev, st.st_ino, save, &dostat);
> -#else
> - name = getttyname ("/dev/pts", st.st_dev, st.st_ino, save, &dostat);
> -#endif
> + name = getttyname ("/dev/pts", &st, save, &dostat);
> }
> else
> {
> @@ -200,21 +186,13 @@ ttyname (int fd)
>
> if (!name && dostat != -1)
> {
> -#ifdef _STATBUF_ST_RDEV
> - name = getttyname ("/dev", st.st_rdev, st.st_ino, save, &dostat);
> -#else
> - name = getttyname ("/dev", st.st_dev, st.st_ino, save, &dostat);
> -#endif
> + name = getttyname ("/dev", &st, save, &dostat);
> }
>
> if (!name && dostat != -1)
> {
> dostat = 1;
> -#ifdef _STATBUF_ST_RDEV
> - name = getttyname ("/dev", st.st_rdev, st.st_ino, save, &dostat);
> -#else
> - name = getttyname ("/dev", st.st_dev, st.st_ino, save, &dostat);
> -#endif
> + name = getttyname ("/dev", &st, save, &dostat);
> }
>
> return name;
> diff --git a/sysdeps/unix/sysv/linux/ttyname.h b/sysdeps/unix/sysv/linux/ttyname.h
> index dd7873d1ff..2b125cfd0b 100644
> --- a/sysdeps/unix/sysv/linux/ttyname.h
> +++ b/sysdeps/unix/sysv/linux/ttyname.h
> @@ -23,7 +23,7 @@
> /* Return true if this is a UNIX98 pty device, as defined in
> linux/Documentation/devices.txt (on linux < 4.10) or
> linux/Documentation/admin-guide/devices.txt (on linux >= 4.10). */
> -static inline int
> +static inline bool
> is_pty (struct stat64 *sb)
> {
> #ifdef _STATBUF_ST_RDEV
> @@ -33,3 +33,15 @@ is_pty (struct stat64 *sb)
> return false;
> #endif
> }
> +
> +static inline bool
> +is_mytty(const struct stat64 *mytty, const struct stat64 *maybe)
> +{
> + return (maybe->st_ino == mytty->st_ino
> + && maybe->st_dev == mytty->st_dev
> +#ifdef _STATBUF_ST_RDEV
> + && S_ISCHR (maybe->st_mode)
> + && maybe->st_rdev == mytty->st_rdev
> +#endif
> + );
> +}
> diff --git a/sysdeps/unix/sysv/linux/ttyname_r.c b/sysdeps/unix/sysv/linux/ttyname_r.c
> index 18f35ef2b7..58eb919c3f 100644
> --- a/sysdeps/unix/sysv/linux/ttyname_r.c
> +++ b/sysdeps/unix/sysv/linux/ttyname_r.c
> @@ -31,12 +31,12 @@
> #include "ttyname.h"
>
> static int getttyname_r (char *buf, size_t buflen,
> - dev_t mydev, ino64_t myino, int save,
> + const struct stat64 *mytty, int save,
> int *dostat);
>
> static int
> attribute_compat_text_section
> -getttyname_r (char *buf, size_t buflen, dev_t mydev, ino64_t myino,
> +getttyname_r (char *buf, size_t buflen, const struct stat64 *mytty,
> int save, int *dostat)
> {
> struct stat64 st;
> @@ -52,7 +52,7 @@ getttyname_r (char *buf, size_t buflen, dev_t mydev, ino64_t myino,
> }
>
> while ((d = __readdir64 (dirstream)) != NULL)
> - if ((d->d_fileno == myino || *dostat)
> + if ((d->d_fileno == mytty->st_ino || *dostat)
> && strcmp (d->d_name, "stdin")
> && strcmp (d->d_name, "stdout")
> && strcmp (d->d_name, "stderr"))
> @@ -72,12 +72,7 @@ getttyname_r (char *buf, size_t buflen, dev_t mydev, ino64_t myino,
> cp[0] = '\0';
>
> if (__xstat64 (_STAT_VER, buf, &st) == 0
> -#ifdef _STATBUF_ST_RDEV
> - && S_ISCHR (st.st_mode) && st.st_rdev == mydev
> -#else
> - && d->d_fileno == myino && st.st_dev == mydev
> -#endif
> - )
> + && is_mytty (mytty, &st))
> {
> (void) __closedir (dirstream);
> __set_errno (save);
> @@ -151,12 +146,7 @@ __ttyname_r (int fd, char *buf, size_t buflen)
> /* Verify readlink result, fall back on iterating through devices. */
> if (buf[0] == '/'
> && __xstat64 (_STAT_VER, buf, &st1) == 0
> -#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)
> + && is_mytty (&st, &st1))
> return 0;
>
> /* If the link doesn't exist, then it points to a device in another
> @@ -175,13 +165,8 @@ __ttyname_r (int fd, char *buf, size_t buflen)
>
> if (__xstat64 (_STAT_VER, buf, &st1) == 0 && S_ISDIR (st1.st_mode))
> {
> -#ifdef _STATBUF_ST_RDEV
> - ret = getttyname_r (buf, buflen, st.st_rdev, st.st_ino, save,
> + ret = getttyname_r (buf, buflen, &st, save,
> &dostat);
> -#else
> - ret = getttyname_r (buf, buflen, st.st_dev, st.st_ino, save,
> - &dostat);
> -#endif
> }
> else
> {
> @@ -193,26 +178,16 @@ __ttyname_r (int fd, char *buf, size_t buflen)
> {
> buf[sizeof ("/dev/") - 1] = '\0';
> buflen += sizeof ("pts/") - 1;
> -#ifdef _STATBUF_ST_RDEV
> - ret = getttyname_r (buf, buflen, st.st_rdev, st.st_ino, save,
> - &dostat);
> -#else
> - ret = getttyname_r (buf, buflen, st.st_dev, st.st_ino, save,
> + ret = getttyname_r (buf, buflen, &st, save,
> &dostat);
> -#endif
> }
>
> if (ret && dostat != -1)
> {
> buf[sizeof ("/dev/") - 1] = '\0';
> dostat = 1;
> -#ifdef _STATBUF_ST_RDEV
> - ret = getttyname_r (buf, buflen, st.st_rdev, st.st_ino,
> - save, &dostat);
> -#else
> - ret = getttyname_r (buf, buflen, st.st_dev, st.st_ino,
> + ret = getttyname_r (buf, buflen, &st,
> save, &dostat);
> -#endif
> }
>
> return ret;
> --
> 2.15.0
>