[v6] vfprintf-internal: Get rid of alloca.
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Commit Message
Avoid potential stack overflow from unbounded alloca. Use the existing
scratch_buffer instead.
Add testcases to exercise the code as suggested by Adhemerval Zanella Netto.
---
Changes to v5:
* Remove unneeded printf and add more tests for various argument
counts.
stdio-common/tst-vfprintf-user-type.c | 130 ++++++++++++++++++++++++++
stdio-common/vfprintf-internal.c | 23 ++++-
2 files changed, 152 insertions(+), 1 deletion(-)
Comments
On 20/07/23 10:44, Joe Simmons-Talbott via Libc-alpha wrote:
> Avoid potential stack overflow from unbounded alloca. Use the existing
> scratch_buffer instead.
>
> Add testcases to exercise the code as suggested by Adhemerval Zanella Netto.
LGTM, thanks.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
> ---
> Changes to v5:
> * Remove unneeded printf and add more tests for various argument
> counts.
>
> stdio-common/tst-vfprintf-user-type.c | 130 ++++++++++++++++++++++++++
> stdio-common/vfprintf-internal.c | 23 ++++-
> 2 files changed, 152 insertions(+), 1 deletion(-)
>
> diff --git a/stdio-common/tst-vfprintf-user-type.c b/stdio-common/tst-vfprintf-user-type.c
> index 7cc69dc716..adcbf33c20 100644
> --- a/stdio-common/tst-vfprintf-user-type.c
> +++ b/stdio-common/tst-vfprintf-user-type.c
> @@ -194,6 +194,136 @@ do_test (void)
> TEST_COMPARE_STRING (str, "[[(123, 457.000000) (123, 457.000000)]]");
> free (str);
>
> + str = NULL;
> + TEST_VERIFY (asprintf_alias (&str, "%1$P %2$P %3$P %4$P %5$P %6$P",
> + 1L, 1.0,
> + 2L, 2.0,
> + 3L, 3.0,
> + 4L, 4.0,
> + 5L, 6.0,
> + 6L, 6.0)
> + >= 0);
> + free (str);
> +
> + str = NULL;
> + TEST_VERIFY (asprintf_alias (&str, "%1$P %2$P %3$P %4$P %5$P %6$P"
> + "%7$P %8$P %9$P %10$P %11$P %12$P",
> + 1L, 1.0,
> + 2L, 2.0,
> + 3L, 3.0,
> + 4L, 4.0,
> + 5L, 6.0,
> + 6L, 6.0,
> + 7L, 7.0,
> + 8L, 8.0,
> + 9L, 9.0,
> + 10L, 10.0,
> + 11L, 11.0,
> + 12L, 12.0)
> + >= 0);
> + free (str);
> +
> + str = NULL;
> + TEST_VERIFY (asprintf_alias (&str, "%1$P %2$P %3$P %4$P %5$P %6$P"
> + "%7$P %8$P %9$P %10$P %11$P %12$P"
> + "%13$P %14$P %15$P %16$P %17$P %18$P",
> + 1L, 1.0,
> + 2L, 2.0,
> + 3L, 3.0,
> + 4L, 4.0,
> + 5L, 6.0,
> + 6L, 6.0,
> + 7L, 7.0,
> + 8L, 8.0,
> + 9L, 9.0,
> + 10L, 10.0,
> + 11L, 11.0,
> + 12L, 12.0,
> + 13L, 13.0,
> + 14L, 14.0,
> + 15L, 15.0,
> + 16L, 16.0,
> + 17L, 17.0,
> + 18L, 18.0)
> + >= 0);
> + free (str);
> +
> + str = NULL;
> + TEST_VERIFY (asprintf_alias (&str, "%1$P %2$P %3$P %4$P %5$P %6$P"
> + "%7$P %8$P %9$P %10$P %11$P %12$P"
> + "%13$P %14$P %15$P %16$P %17$P %18$P"
> + "%19$P %20$P %21$P %22$P %23$P %24$P",
> + 1L, 1.0,
> + 2L, 2.0,
> + 3L, 3.0,
> + 4L, 4.0,
> + 5L, 6.0,
> + 6L, 6.0,
> + 7L, 7.0,
> + 8L, 8.0,
> + 9L, 9.0,
> + 10L, 10.0,
> + 11L, 11.0,
> + 12L, 12.0,
> + 13L, 13.0,
> + 14L, 14.0,
> + 15L, 15.0,
> + 16L, 16.0,
> + 17L, 17.0,
> + 18L, 18.0,
> + 19L, 19.0,
> + 20L, 20.0,
> + 21L, 21.0,
> + 22L, 22.0,
> + 23L, 23.0,
> + 24L, 24.0)
> + >= 0);
> + free (str);
> +
> + str = NULL;
> + TEST_VERIFY (asprintf_alias (&str, "%1$P %2$P %3$P %4$P %5$P %6$P"
> + "%7$P %8$P %9$P %10$P %11$P %12$P"
> + "%13$P %14$P %15$P %16$P %17$P %18$P"
> + "%19$P %20$P %21$P %22$P %23$P %24$P"
> + "%25$P %26$P %27$P %28$P %29$P %30$P",
> + 1L, 1.0,
> + 2L, 2.0,
> + 3L, 3.0,
> + 4L, 4.0,
> + 5L, 6.0,
> + 6L, 6.0,
> + 7L, 7.0,
> + 8L, 8.0,
> + 9L, 9.0,
> + 10L, 10.0,
> + 11L, 11.0,
> + 12L, 12.0,
> + 13L, 13.0,
> + 14L, 14.0,
> + 15L, 15.0,
> + 16L, 16.0,
> + 17L, 17.0,
> + 18L, 18.0,
> + 19L, 19.0,
> + 20L, 20.0,
> + 21L, 21.0,
> + 22L, 22.0,
> + 23L, 23.0,
> + 24L, 34.0,
> + 25L, 25.0,
> + 26L, 26.0,
> + 27L, 27.0,
> + 28L, 28.0,
> + 29L, 29.0,
> + 30, 30.0)
> + >= 0);
> + free (str);
> +
> + str = NULL;
> + TEST_VERIFY (asprintf_alias (&str, "[[%1$P %1$P]]", 123L, 457.0) >= 0);
> + TEST_COMPARE_STRING (str, "[[(123, 457.000000) (123, 457.000000)]]");
> + free (str);
> +
> str = NULL;
> TEST_VERIFY (asprintf_alias (&str, "[[%.1P]]", 1L, 2.0) >= 0);
> TEST_COMPARE_STRING (str, "[[{(1, 2.000000)}]]");
> diff --git a/stdio-common/vfprintf-internal.c b/stdio-common/vfprintf-internal.c
> index f30a9e9f3a..6d6d96e800 100644
> --- a/stdio-common/vfprintf-internal.c
> +++ b/stdio-common/vfprintf-internal.c
> @@ -1130,6 +1130,8 @@ printf_positional (struct Xprintf_buffer * buf, const CHAR_T *format,
> union printf_arg *args_value;
> int *args_size;
> int *args_type;
> + void *args_pa_user;
> + size_t args_pa_user_offset;
> {
> /* Calculate total size needed to represent a single argument
> across all three argument-related arrays. */
> @@ -1146,6 +1148,7 @@ printf_positional (struct Xprintf_buffer * buf, const CHAR_T *format,
> now. */
> args_size = &args_value[nargs].pa_int;
> args_type = &args_size[nargs];
> + args_pa_user = &args_type[nargs];
> memset (args_type, (mode_flags & PRINTF_FORTIFY) != 0 ? '\xff' : '\0',
> nargs * sizeof (*args_type));
> }
> @@ -1235,7 +1238,25 @@ printf_positional (struct Xprintf_buffer * buf, const CHAR_T *format,
> else if (__glibc_unlikely (__printf_va_arg_table != NULL)
> && __printf_va_arg_table[args_type[cnt] - PA_LAST] != NULL)
> {
> - args_value[cnt].pa_user = alloca (args_size[cnt]);
> + while (args_pa_user + args_size[cnt] >
> + argsbuf.data + argsbuf.length)
> + {
> + args_pa_user_offset = args_pa_user - (void *) &args_type[nargs];
> + if (!scratch_buffer_grow_preserve (&argsbuf))
> + {
> + Xprintf_buffer_mark_failed (buf);
> + goto all_done;
> + }
> + args_value = argsbuf.data;
> + /* Set up the remaining two arrays to each point past the end of
> + the prior array, since space for all three has been allocated
> + now. */
> + args_size = &args_value[nargs].pa_int;
> + args_type = &args_size[nargs];
> + args_pa_user = (void *) &args_type[nargs] + args_pa_user_offset;
> + }
> + args_value[cnt].pa_user = args_pa_user;
> + args_pa_user += args_size[cnt];
> (*__printf_va_arg_table[args_type[cnt] - PA_LAST])
> (args_value[cnt].pa_user, ap_savep);
> }
@@ -194,6 +194,136 @@ do_test (void)
TEST_COMPARE_STRING (str, "[[(123, 457.000000) (123, 457.000000)]]");
free (str);
+ str = NULL;
+ TEST_VERIFY (asprintf_alias (&str, "%1$P %2$P %3$P %4$P %5$P %6$P",
+ 1L, 1.0,
+ 2L, 2.0,
+ 3L, 3.0,
+ 4L, 4.0,
+ 5L, 6.0,
+ 6L, 6.0)
+ >= 0);
+ free (str);
+
+ str = NULL;
+ TEST_VERIFY (asprintf_alias (&str, "%1$P %2$P %3$P %4$P %5$P %6$P"
+ "%7$P %8$P %9$P %10$P %11$P %12$P",
+ 1L, 1.0,
+ 2L, 2.0,
+ 3L, 3.0,
+ 4L, 4.0,
+ 5L, 6.0,
+ 6L, 6.0,
+ 7L, 7.0,
+ 8L, 8.0,
+ 9L, 9.0,
+ 10L, 10.0,
+ 11L, 11.0,
+ 12L, 12.0)
+ >= 0);
+ free (str);
+
+ str = NULL;
+ TEST_VERIFY (asprintf_alias (&str, "%1$P %2$P %3$P %4$P %5$P %6$P"
+ "%7$P %8$P %9$P %10$P %11$P %12$P"
+ "%13$P %14$P %15$P %16$P %17$P %18$P",
+ 1L, 1.0,
+ 2L, 2.0,
+ 3L, 3.0,
+ 4L, 4.0,
+ 5L, 6.0,
+ 6L, 6.0,
+ 7L, 7.0,
+ 8L, 8.0,
+ 9L, 9.0,
+ 10L, 10.0,
+ 11L, 11.0,
+ 12L, 12.0,
+ 13L, 13.0,
+ 14L, 14.0,
+ 15L, 15.0,
+ 16L, 16.0,
+ 17L, 17.0,
+ 18L, 18.0)
+ >= 0);
+ free (str);
+
+ str = NULL;
+ TEST_VERIFY (asprintf_alias (&str, "%1$P %2$P %3$P %4$P %5$P %6$P"
+ "%7$P %8$P %9$P %10$P %11$P %12$P"
+ "%13$P %14$P %15$P %16$P %17$P %18$P"
+ "%19$P %20$P %21$P %22$P %23$P %24$P",
+ 1L, 1.0,
+ 2L, 2.0,
+ 3L, 3.0,
+ 4L, 4.0,
+ 5L, 6.0,
+ 6L, 6.0,
+ 7L, 7.0,
+ 8L, 8.0,
+ 9L, 9.0,
+ 10L, 10.0,
+ 11L, 11.0,
+ 12L, 12.0,
+ 13L, 13.0,
+ 14L, 14.0,
+ 15L, 15.0,
+ 16L, 16.0,
+ 17L, 17.0,
+ 18L, 18.0,
+ 19L, 19.0,
+ 20L, 20.0,
+ 21L, 21.0,
+ 22L, 22.0,
+ 23L, 23.0,
+ 24L, 24.0)
+ >= 0);
+ free (str);
+
+ str = NULL;
+ TEST_VERIFY (asprintf_alias (&str, "%1$P %2$P %3$P %4$P %5$P %6$P"
+ "%7$P %8$P %9$P %10$P %11$P %12$P"
+ "%13$P %14$P %15$P %16$P %17$P %18$P"
+ "%19$P %20$P %21$P %22$P %23$P %24$P"
+ "%25$P %26$P %27$P %28$P %29$P %30$P",
+ 1L, 1.0,
+ 2L, 2.0,
+ 3L, 3.0,
+ 4L, 4.0,
+ 5L, 6.0,
+ 6L, 6.0,
+ 7L, 7.0,
+ 8L, 8.0,
+ 9L, 9.0,
+ 10L, 10.0,
+ 11L, 11.0,
+ 12L, 12.0,
+ 13L, 13.0,
+ 14L, 14.0,
+ 15L, 15.0,
+ 16L, 16.0,
+ 17L, 17.0,
+ 18L, 18.0,
+ 19L, 19.0,
+ 20L, 20.0,
+ 21L, 21.0,
+ 22L, 22.0,
+ 23L, 23.0,
+ 24L, 34.0,
+ 25L, 25.0,
+ 26L, 26.0,
+ 27L, 27.0,
+ 28L, 28.0,
+ 29L, 29.0,
+ 30, 30.0)
+ >= 0);
+ free (str);
+
+ str = NULL;
+ TEST_VERIFY (asprintf_alias (&str, "[[%1$P %1$P]]", 123L, 457.0) >= 0);
+ TEST_COMPARE_STRING (str, "[[(123, 457.000000) (123, 457.000000)]]");
+ free (str);
+
str = NULL;
TEST_VERIFY (asprintf_alias (&str, "[[%.1P]]", 1L, 2.0) >= 0);
TEST_COMPARE_STRING (str, "[[{(1, 2.000000)}]]");
@@ -1130,6 +1130,8 @@ printf_positional (struct Xprintf_buffer * buf, const CHAR_T *format,
union printf_arg *args_value;
int *args_size;
int *args_type;
+ void *args_pa_user;
+ size_t args_pa_user_offset;
{
/* Calculate total size needed to represent a single argument
across all three argument-related arrays. */
@@ -1146,6 +1148,7 @@ printf_positional (struct Xprintf_buffer * buf, const CHAR_T *format,
now. */
args_size = &args_value[nargs].pa_int;
args_type = &args_size[nargs];
+ args_pa_user = &args_type[nargs];
memset (args_type, (mode_flags & PRINTF_FORTIFY) != 0 ? '\xff' : '\0',
nargs * sizeof (*args_type));
}
@@ -1235,7 +1238,25 @@ printf_positional (struct Xprintf_buffer * buf, const CHAR_T *format,
else if (__glibc_unlikely (__printf_va_arg_table != NULL)
&& __printf_va_arg_table[args_type[cnt] - PA_LAST] != NULL)
{
- args_value[cnt].pa_user = alloca (args_size[cnt]);
+ while (args_pa_user + args_size[cnt] >
+ argsbuf.data + argsbuf.length)
+ {
+ args_pa_user_offset = args_pa_user - (void *) &args_type[nargs];
+ if (!scratch_buffer_grow_preserve (&argsbuf))
+ {
+ Xprintf_buffer_mark_failed (buf);
+ goto all_done;
+ }
+ args_value = argsbuf.data;
+ /* Set up the remaining two arrays to each point past the end of
+ the prior array, since space for all three has been allocated
+ now. */
+ args_size = &args_value[nargs].pa_int;
+ args_type = &args_size[nargs];
+ args_pa_user = (void *) &args_type[nargs] + args_pa_user_offset;
+ }
+ args_value[cnt].pa_user = args_pa_user;
+ args_pa_user += args_size[cnt];
(*__printf_va_arg_table[args_type[cnt] - PA_LAST])
(args_value[cnt].pa_user, ap_savep);
}