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2fbce9c203
In the ttyname and ttyname_r routines on Linux, at several points it needs to
check if a given TTY is the TTY we are looking for. It used to be that this
check 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, one of the changes made in commit 15e9a4f378
was to change that check 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, it made the st_ino and st_dev parts of the check happen even if we have
the st_rdev member. This is an important change, because the kernel allows
multiple devpts filesystem instances to be created; a device file in one devpts
instance may share the same st_rdev with a file in another devpts instance, but
they aren't the same file.
This check appears twice in each file (ttyname.c and ttyname_r.c), once (in
ttyname and __ttyname_r) to check if a candidate file found by inspecting /proc
is the desired TTY, and once (in getttyname and getttyname_r) to check if a
candidate file found by searching /dev is the desired TTY. However, 15e9a4f
only updated the checks for files found via /proc; but the concern about
collisions between devpts instances is just as valid for files found via /dev.
So, update all 4 occurrences the check to be consistent with the version of the
check introduced in 15e9a4f. Make it easy to keep all 4 occurrences of the
check consistent by pulling it in to a static inline function, is_mytty.
Reviewed-by: Christian Brauner <christian.brauner@ubuntu.com>
49 lines
1.5 KiB
C
49 lines
1.5 KiB
C
/* Copyright (C) 2016-2017 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public License as
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published by the Free Software Foundation; either version 2.1 of the
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License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; see the file COPYING.LIB. If
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not, see <http://www.gnu.org/licenses/>. */
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#include <unistd.h>
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#include <stdbool.h>
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#include <sys/sysmacros.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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/* Return true if this is a UNIX98 pty device, as defined in
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linux/Documentation/devices.txt (on linux < 4.10) or
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linux/Documentation/admin-guide/devices.txt (on linux >= 4.10). */
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static inline bool
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is_pty (struct stat64 *sb)
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{
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#ifdef _STATBUF_ST_RDEV
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int m = major (sb->st_rdev);
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return (136 <= m && m <= 143);
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#else
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return false;
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#endif
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}
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static inline bool
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is_mytty (const struct stat64 *mytty, const struct stat64 *maybe)
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{
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return (maybe->st_ino == mytty->st_ino
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&& maybe->st_dev == mytty->st_dev
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#ifdef _STATBUF_ST_RDEV
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&& S_ISCHR (maybe->st_mode)
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&& maybe->st_rdev == mytty->st_rdev
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#endif
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);
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}
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