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From: Joe Simmons-Talbott <josepht@sourceware.org> To: glibc-cvs@sourceware.org Subject: [glibc] vfprintf-internal: Get rid of alloca. Date: Tue, 1 Aug 2023 12:33:02 +0000 (GMT) [thread overview] Message-ID: <20230801123302.0F33C3858D28@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=5c37d2065286d3db7b974266a3002bb5747d2e5d commit 5c37d2065286d3db7b974266a3002bb5747d2e5d Author: Joe Simmons-Talbott <josimmon@redhat.com> Date: Mon Jul 31 19:42:32 2023 +0000 vfprintf-internal: Get rid of alloca. 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. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org> Diff: --- 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); }
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