Message ID | 20230620132644.2984023-1-josimmon@redhat.com |
---|---|
State | New |
Headers | show |
Series | [v5] vfprintf-internal: Get rid of alloca. | expand |
On Tue, Jun 20, 2023 at 09:26:44AM -0400, Joe Simmons-Talbott wrote: > Avoid potential stack overflow from unbounded alloca. Use the existing > scratch_buffer instead. > > Add a testcase to exercise the code as suggested by Adhemerval Zanella Netto. > --- > Changes to v4: > * Rebased to latest commits. Ping. Thanks, Joe
On 20/06/23 10:26, Joe Simmons-Talbott via Libc-alpha wrote: > Avoid potential stack overflow from unbounded alloca. Use the existing > scratch_buffer instead. > > Add a testcase to exercise the code as suggested by Adhemerval Zanella Netto. > --- > Changes to v4: > * Rebased to latest commits. > > stdio-common/tst-vfprintf-user-type.c | 43 +++++++++++++++++++++++++++ > stdio-common/vfprintf-internal.c | 23 +++++++++++++- > 2 files changed, 65 insertions(+), 1 deletion(-) > > diff --git a/stdio-common/tst-vfprintf-user-type.c b/stdio-common/tst-vfprintf-user-type.c > index 7cc69dc716..bd2ac04351 100644 > --- a/stdio-common/tst-vfprintf-user-type.c > +++ b/stdio-common/tst-vfprintf-user-type.c > @@ -194,6 +194,49 @@ 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" > + "%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) > + >= 0); > + printf ("str=%s\n", str); Remove the printf, I added while debugging. > + 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)}]]"); Could you tune the test to check for multiple different argument numbers? I added 28 to be assured that the printf_positional path were triggered, but it wold be good to test for different argument numbers as well. > 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); > }
On Wed, Jul 19, 2023 at 03:04:09PM -0300, Adhemerval Zanella Netto wrote: > > > On 20/06/23 10:26, Joe Simmons-Talbott via Libc-alpha wrote: > > Avoid potential stack overflow from unbounded alloca. Use the existing > > scratch_buffer instead. > > > > Add a testcase to exercise the code as suggested by Adhemerval Zanella Netto. > > --- > > Changes to v4: > > * Rebased to latest commits. > > > > stdio-common/tst-vfprintf-user-type.c | 43 +++++++++++++++++++++++++++ > > stdio-common/vfprintf-internal.c | 23 +++++++++++++- > > 2 files changed, 65 insertions(+), 1 deletion(-) > > > > diff --git a/stdio-common/tst-vfprintf-user-type.c b/stdio-common/tst-vfprintf-user-type.c > > index 7cc69dc716..bd2ac04351 100644 > > --- a/stdio-common/tst-vfprintf-user-type.c > > +++ b/stdio-common/tst-vfprintf-user-type.c > > @@ -194,6 +194,49 @@ 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" > > + "%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) > > + >= 0); > > + printf ("str=%s\n", str); > > Remove the printf, I added while debugging. > Done in v6. > > + 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)}]]"); > > Could you tune the test to check for multiple different argument numbers? I added > 28 to be assured that the printf_positional path were triggered, but it wold be > good to test for different argument numbers as well. For v6 I did checks in groups of 6 from 6 to 30. If that doesn't seem sufficient please let me know. Thanks for the review. Thanks, Joe > > > 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); > > } >
diff --git a/stdio-common/tst-vfprintf-user-type.c b/stdio-common/tst-vfprintf-user-type.c index 7cc69dc716..bd2ac04351 100644 --- a/stdio-common/tst-vfprintf-user-type.c +++ b/stdio-common/tst-vfprintf-user-type.c @@ -194,6 +194,49 @@ 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" + "%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) + >= 0); + printf ("str=%s\n", str); + 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); }