[v2,07/19] elf: Fix _dl_debug_vdprintf to work before self-relocation
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Commit Message
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).
Checked on x86_64-linux-gnu.
---
elf/dl-printf.c | 16 ++++++++++++++--
stdio-common/Makefile | 5 +++++
stdio-common/_itoa.c | 5 +++++
3 files changed, 24 insertions(+), 2 deletions(-)
Comments
On 2023-10-17 09:05, Adhemerval Zanella wrote:
> 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).
>
> Checked on x86_64-linux-gnu.
> ---
LGTM.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
> elf/dl-printf.c | 16 ++++++++++++++--
> stdio-common/Makefile | 5 +++++
> stdio-common/_itoa.c | 5 +++++
> 3 files changed, 24 insertions(+), 2 deletions(-)
>
> 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>
@@ -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;
@@ -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.
@@ -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>