From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
To: libc-alpha@sourceware.org, Siddhesh Poyarekar <siddhesh@sourceware.org>
Subject: [PATCH v3 07/19] elf: Fix _dl_debug_vdprintf to work before self-relocation
Date: Mon, 6 Nov 2023 17:25:40 -0300 [thread overview]
Message-ID: <20231106202552.3404059-8-adhemerval.zanella@linaro.org> (raw)
In-Reply-To: <20231106202552.3404059-1-adhemerval.zanella@linaro.org>
The strlen might trigger and invalid GOT entry if it used before
the process is self-relocated (for instance on dl-tunables if any
error occurs).
For i386, _dl_writev with PIE requires to use the old 'int $0x80'
syscall mode because the calling the TLS register (gs) is not yet
initialized.
Checked on x86_64-linux-gnu.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
---
elf/dl-printf.c | 16 ++++++++++++++--
stdio-common/Makefile | 5 +++++
stdio-common/_itoa.c | 5 +++++
sysdeps/unix/sysv/linux/i386/dl-writev.h | 24 ++++++++++++++++++++++++
4 files changed, 48 insertions(+), 2 deletions(-)
create mode 100644 sysdeps/unix/sysv/linux/i386/dl-writev.h
diff --git a/elf/dl-printf.c b/elf/dl-printf.c
index 6efb4c019a..5e93208535 100644
--- a/elf/dl-printf.c
+++ b/elf/dl-printf.c
@@ -17,6 +17,10 @@
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
+#include <string.h>
+#if BUILD_PIE_DEFAULT
+# pragma GCC visibility push(hidden)
+#endif
#include <_itoa.h>
#include <assert.h>
#include <dl-writev.h>
@@ -25,11 +29,19 @@
#include <stdarg.h>
#include <stdint.h>
#include <stdlib.h>
-#include <string.h>
#include <sys/uio.h>
#include <unistd.h>
#include <intprops.h>
+/* The function might be called before the process is self-relocated. */
+static size_t
+_dl_debug_strlen (const char *s)
+{
+ const char *p = s;
+ for (; *s != '\0'; s++);
+ return s - p;
+}
+
/* Bare-bones printf implementation. This function only knows about
the formats and flags needed and can handle only up to 64 stripes in
the output. */
@@ -193,7 +205,7 @@ _dl_debug_vdprintf (int fd, int tag_p, const char *fmt, va_list arg)
case 's':
/* Get the string argument. */
iov[niov].iov_base = va_arg (arg, char *);
- iov[niov].iov_len = strlen (iov[niov].iov_base);
+ iov[niov].iov_len = _dl_debug_strlen (iov[niov].iov_base);
if (prec != -1)
iov[niov].iov_len = MIN ((size_t) prec, iov[niov].iov_len);
++niov;
diff --git a/stdio-common/Makefile b/stdio-common/Makefile
index bacb795fed..e88a9cea29 100644
--- a/stdio-common/Makefile
+++ b/stdio-common/Makefile
@@ -460,6 +460,11 @@ CFLAGS-isoc23_scanf.c += -fexceptions
CFLAGS-dprintf.c += $(config-cflags-wno-ignored-attributes)
+# Called during static library initialization, so turn stack-protection
+# off for non-shared builds.
+CFLAGS-_itoa.o = $(no-stack-protector)
+CFLAGS-_itoa.op = $(no-stack-protector)
+
# scanf18.c and scanf19.c test a deprecated extension which is no
# longer visible under most conformance levels; see the source files
# for more detail.
diff --git a/stdio-common/_itoa.c b/stdio-common/_itoa.c
index 3037b0f529..48f2903ecb 100644
--- a/stdio-common/_itoa.c
+++ b/stdio-common/_itoa.c
@@ -16,6 +16,11 @@
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
+/* Mark symbols hidden in static PIE for early self relocation to work.
+ Note: string.h may have ifuncs which cannot be hidden on i686. */
+#if BUILD_PIE_DEFAULT
+# pragma GCC visibility push(hidden)
+#endif
#include <gmp-mparam.h>
#include <gmp.h>
#include <limits.h>
diff --git a/sysdeps/unix/sysv/linux/i386/dl-writev.h b/sysdeps/unix/sysv/linux/i386/dl-writev.h
new file mode 100644
index 0000000000..624d0e46b0
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/i386/dl-writev.h
@@ -0,0 +1,24 @@
+/* Message-writing for the dynamic linker. Linux/i386 version.
+ Copyright (C) 2013-2023 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#if BUILD_PIE_DEFAULT
+/* Can't use "call *%gs:SYSINFO_OFFSET" during startup in static PIE. */
+# define I386_USE_SYSENTER 0
+#endif
+
+#include <sysdeps/unix/sysv/linux/dl-writev.h>
--
2.34.1
next prev parent reply other threads:[~2023-11-06 20:26 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-06 20:25 [PATCH v3 00/19] Improve loader environment variable handling Adhemerval Zanella
2023-11-06 20:25 ` [PATCH v3 01/19] elf: Remove /etc/suid-debug support Adhemerval Zanella
2023-11-06 20:25 ` [PATCH v3 02/19] elf: Add GLIBC_TUNABLES to unsecvars Adhemerval Zanella
2023-11-06 20:25 ` [PATCH v3 03/19] elf: Ignore GLIBC_TUNABLES for setuid/setgid binaries Adhemerval Zanella
2023-11-06 20:25 ` [PATCH v3 04/19] elf: Add all malloc tunable to unsecvars Adhemerval Zanella
2023-11-06 20:25 ` [PATCH v3 05/19] elf: Do not process invalid tunable format Adhemerval Zanella
2023-11-06 20:25 ` [PATCH v3 06/19] elf: Do not parse ill-formatted strings Adhemerval Zanella
2023-11-20 21:48 ` Siddhesh Poyarekar
2023-11-06 20:25 ` Adhemerval Zanella [this message]
2023-11-06 20:25 ` [PATCH v3 08/19] elf: Emit warning if tunable is ill-formatted Adhemerval Zanella
2023-11-20 21:50 ` Siddhesh Poyarekar
2023-11-06 20:25 ` [PATCH v3 09/19] x86: Use dl-symbol-redir-ifunc.h on cpu-tunables Adhemerval Zanella
2023-11-06 20:25 ` [PATCH v3 10/19] s390: " Adhemerval Zanella
2023-11-06 20:25 ` [PATCH v3 11/19] elf: Do not duplicate the GLIBC_TUNABLES string Adhemerval Zanella
2023-11-20 22:44 ` Siddhesh Poyarekar
2023-11-21 18:12 ` Adhemerval Zanella Netto
2023-11-22 11:39 ` Adhemerval Zanella Netto
2023-11-22 12:23 ` Siddhesh Poyarekar
2023-11-22 13:03 ` Adhemerval Zanella Netto
2023-11-22 13:24 ` Siddhesh Poyarekar
2023-11-22 14:13 ` Adhemerval Zanella Netto
2023-11-06 20:25 ` [PATCH v3 12/19] elf: Ignore LD_PROFILE for setuid binaries Adhemerval Zanella
2023-11-20 22:47 ` Siddhesh Poyarekar
2023-11-06 20:25 ` [PATCH v3 13/19] elf: Remove LD_PROFILE for static binaries Adhemerval Zanella
2023-11-20 22:55 ` Siddhesh Poyarekar
2023-11-06 20:25 ` [PATCH v3 14/19] elf: Ignore loader debug env vars for setuid Adhemerval Zanella
2023-11-20 22:57 ` Siddhesh Poyarekar
2023-11-21 18:24 ` Adhemerval Zanella Netto
2023-11-06 20:25 ` [PATCH v3 15/19] elf: Remove any_debug from dl_main_state Adhemerval Zanella
2023-11-20 22:58 ` Siddhesh Poyarekar
2023-11-06 20:25 ` [PATCH v3 16/19] elf: Ignore LD_LIBRARY_PATH and debug env var for setuid for static Adhemerval Zanella
2023-11-20 22:59 ` Siddhesh Poyarekar
2023-11-06 20:25 ` [PATCH v3 17/19] elf: Add comments on how LD_AUDIT and LD_PRELOAD handle __libc_enable_secure Adhemerval Zanella
2023-11-06 20:25 ` [PATCH v3 18/19] elf: Ignore LD_BIND_NOW and LD_BIND_NOT for setuid binaries Adhemerval Zanella
2023-11-20 23:02 ` Siddhesh Poyarekar
2023-11-06 20:25 ` [PATCH v3 19/19] elf: Refactor process_envvars Adhemerval Zanella
2023-11-20 23:09 ` Siddhesh Poyarekar
2023-11-21 19:00 ` Adhemerval Zanella Netto
2023-11-20 23:12 ` [PATCH v3 00/19] Improve loader environment variable handling Siddhesh Poyarekar
2023-11-21 19:37 ` Adhemerval Zanella Netto
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