* [PATCH] malloc_stats(): Fix `unsigned int` overflow
@ 2021-10-29 17:11 Niklas Hambüchen
2021-10-29 19:50 ` DJ Delorie
0 siblings, 1 reply; 10+ messages in thread
From: Niklas Hambüchen @ 2021-10-29 17:11 UTC (permalink / raw)
To: libc-alpha
Fixes malloc_stats() returning vastly wrong information for programs
that use more than 2 GiB memory.
`man mallinfo` documents that it uses `int` and wraps around, but
`man malloc_stats` does not, and should not.
Fixes https://sourceware.org/bugzilla/show_bug.cgi?id=21556
Signed-off-by: Niklas Hambüchen <mail@nh2.me>
---
malloc/malloc.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/malloc/malloc.c b/malloc/malloc.c
index 095d97a3be..cdc9aff9d5 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -5151,7 +5151,7 @@ __malloc_stats (void)
{
int i;
mstate ar_ptr;
- unsigned int in_use_b = mp_.mmapped_mem, system_b = in_use_b;
+ size_t in_use_b = mp_.mmapped_mem, system_b = in_use_b;
if (!__malloc_initialized)
ptmalloc_init ();
@@ -5166,8 +5166,8 @@ __malloc_stats (void)
__libc_lock_lock (ar_ptr->mutex);
int_mallinfo (ar_ptr, &mi);
fprintf (stderr, "Arena %d:\n", i);
- fprintf (stderr, "system bytes = %10u\n", (unsigned int) mi.arena);
- fprintf (stderr, "in use bytes = %10u\n", (unsigned int) mi.uordblks);
+ fprintf (stderr, "system bytes = %10lu\n", mi.arena);
+ fprintf (stderr, "in use bytes = %10lu\n", mi.uordblks);
#if MALLOC_DEBUG > 1
if (i > 0)
dump_heap (heap_for_ptr (top (ar_ptr)));
@@ -5180,9 +5180,9 @@ __malloc_stats (void)
break;
}
fprintf (stderr, "Total (incl. mmap):\n");
- fprintf (stderr, "system bytes = %10u\n", system_b);
- fprintf (stderr, "in use bytes = %10u\n", in_use_b);
- fprintf (stderr, "max mmap regions = %10u\n", (unsigned int) mp_.max_n_mmaps);
+ fprintf (stderr, "system bytes = %10lu\n", system_b);
+ fprintf (stderr, "in use bytes = %10lu\n", in_use_b);
+ fprintf (stderr, "max mmap regions = %10d\n", mp_.max_n_mmaps);
fprintf (stderr, "max mmap bytes = %10lu\n",
(unsigned long) mp_.max_mmapped_mem);
stderr->_flags2 = old_flags2;
--
2.31.1
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] malloc_stats(): Fix `unsigned int` overflow
2021-10-29 17:11 [PATCH] malloc_stats(): Fix `unsigned int` overflow Niklas Hambüchen
@ 2021-10-29 19:50 ` DJ Delorie
2021-10-30 0:36 ` Niklas Hambüchen
0 siblings, 1 reply; 10+ messages in thread
From: DJ Delorie @ 2021-10-29 19:50 UTC (permalink / raw)
To: Niklas Hambüchen; +Cc: libc-alpha
Fails 32-bit build:
https://www.delorie.com/trybots/32bit/4291/make.tail.txt
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] malloc_stats(): Fix `unsigned int` overflow
2021-10-29 19:50 ` DJ Delorie
@ 2021-10-30 0:36 ` Niklas Hambüchen
2021-10-30 1:39 ` Siddhesh Poyarekar
` (2 more replies)
0 siblings, 3 replies; 10+ messages in thread
From: Niklas Hambüchen @ 2021-10-30 0:36 UTC (permalink / raw)
To: DJ Delorie; +Cc: libc-alpha
The error:
> malloc.c:5169:48: error: format '%lu' expects argument of type 'long unsigned int', but argument 3 has type 'size_t' {aka 'unsigned int'} [-Werror=format=]
glibc doesn't require C99, so I guess "%zu" is not an option, right?
Since this is just in an `fprintf`, would casting to `(unsigned long long)` and using "%llu" be considered acceptable?
Niklas
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] malloc_stats(): Fix `unsigned int` overflow
2021-10-30 0:36 ` Niklas Hambüchen
@ 2021-10-30 1:39 ` Siddhesh Poyarekar
2021-10-30 6:55 ` Andreas Schwab
2021-11-01 12:34 ` [PATCH] " Adhemerval Zanella
2 siblings, 0 replies; 10+ messages in thread
From: Siddhesh Poyarekar @ 2021-10-30 1:39 UTC (permalink / raw)
To: Niklas Hambüchen, DJ Delorie; +Cc: libc-alpha
On 10/30/21 06:06, Niklas Hambüchen via Libc-alpha wrote:
> The error:
>
>> malloc.c:5169:48: error: format '%lu' expects argument of type 'long unsigned int', but argument 3 has type 'size_t' {aka 'unsigned int'} [-Werror=format=]
>
> glibc doesn't require C99, so I guess "%zu" is not an option, right?
%zu is already being used in the file you're changing, so it's perfectly
fine to use.
Siddhesh
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] malloc_stats(): Fix `unsigned int` overflow
2021-10-30 0:36 ` Niklas Hambüchen
2021-10-30 1:39 ` Siddhesh Poyarekar
@ 2021-10-30 6:55 ` Andreas Schwab
2023-11-13 18:27 ` [PATCH v2] " Niklas Hambüchen
2021-11-01 12:34 ` [PATCH] " Adhemerval Zanella
2 siblings, 1 reply; 10+ messages in thread
From: Andreas Schwab @ 2021-10-30 6:55 UTC (permalink / raw)
To: Niklas Hambüchen via Libc-alpha; +Cc: DJ Delorie, Niklas Hambüchen
On Okt 30 2021, Niklas Hambüchen via Libc-alpha wrote:
> glibc doesn't require C99, so I guess "%zu" is not an option, right?
glibc _implements_ C99, so you can use all its features.
Andreas.
--
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510 2552 DF73 E780 A9DA AEC1
"And now for something completely different."
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] malloc_stats(): Fix `unsigned int` overflow
2021-10-30 0:36 ` Niklas Hambüchen
2021-10-30 1:39 ` Siddhesh Poyarekar
2021-10-30 6:55 ` Andreas Schwab
@ 2021-11-01 12:34 ` Adhemerval Zanella
2 siblings, 0 replies; 10+ messages in thread
From: Adhemerval Zanella @ 2021-11-01 12:34 UTC (permalink / raw)
To: libc-alpha
On 29/10/2021 21:36, Niklas Hambüchen via Libc-alpha wrote:
> The error:
>
>> malloc.c:5169:48: error: format '%lu' expects argument of type 'long unsigned int', but argument 3 has type 'size_t' {aka 'unsigned int'} [-Werror=format=]
>
> glibc doesn't require C99, so I guess "%zu" is not an option, right?
We build glibc with -std=gnu11, so we do require a compile that at least support
C11.
>
> Since this is just in an `fprintf`, would casting to `(unsigned long long)` and using "%llu" be considered acceptable?
Either way would be fine.
^ permalink raw reply [flat|nested] 10+ messages in thread
* [PATCH v2] malloc_stats(): Fix `unsigned int` overflow
2021-10-30 6:55 ` Andreas Schwab
@ 2023-11-13 18:27 ` Niklas Hambüchen
2023-11-13 20:25 ` DJ Delorie
0 siblings, 1 reply; 10+ messages in thread
From: Niklas Hambüchen @ 2023-11-13 18:27 UTC (permalink / raw)
To: Niklas Hambüchen via Libc-alpha; +Cc: DJ Delorie, Andreas Schwab
Fixes malloc_stats() returning vastly wrong information for programs
that use more than 2 GiB memory.
`man mallinfo` documents that it uses `int` and wraps around, but
`man malloc_stats` does not, and should not.
Fixes https://sourceware.org/bugzilla/show_bug.cgi?id=21556
Signed-off-by: Niklas Hambüchen <mail@nh2.me>
---
malloc/malloc.c | 15 +++++++--------
1 file changed, 7 insertions(+), 8 deletions(-)
diff --git a/malloc/malloc.c b/malloc/malloc.c
index 78a531bc7a..dfb266a226 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -5374,7 +5374,7 @@ __malloc_stats (void)
{
int i;
mstate ar_ptr;
- unsigned int in_use_b = mp_.mmapped_mem, system_b = in_use_b;
+ size_t in_use_b = mp_.mmapped_mem, system_b = in_use_b;
if (!__malloc_initialized)
ptmalloc_init ();
@@ -5389,8 +5389,8 @@ __malloc_stats (void)
__libc_lock_lock (ar_ptr->mutex);
int_mallinfo (ar_ptr, &mi);
fprintf (stderr, "Arena %d:\n", i);
- fprintf (stderr, "system bytes = %10u\n", (unsigned int) mi.arena);
- fprintf (stderr, "in use bytes = %10u\n", (unsigned int) mi.uordblks);
+ fprintf (stderr, "system bytes = %10zu\n", mi.arena);
+ fprintf (stderr, "in use bytes = %10zu\n", mi.uordblks);
#if MALLOC_DEBUG > 1
if (i > 0)
dump_heap (heap_for_ptr (top (ar_ptr)));
@@ -5403,11 +5403,10 @@ __malloc_stats (void)
break;
}
fprintf (stderr, "Total (incl. mmap):\n");
- fprintf (stderr, "system bytes = %10u\n", system_b);
- fprintf (stderr, "in use bytes = %10u\n", in_use_b);
- fprintf (stderr, "max mmap regions = %10u\n", (unsigned int) mp_.max_n_mmaps);
- fprintf (stderr, "max mmap bytes = %10lu\n",
- (unsigned long) mp_.max_mmapped_mem);
+ fprintf (stderr, "system bytes = %10zu\n", system_b);
+ fprintf (stderr, "in use bytes = %10zu\n", in_use_b);
+ fprintf (stderr, "max mmap regions = %10d\n", mp_.max_n_mmaps);
+ fprintf (stderr, "max mmap bytes = %10zu\n", mp_.max_mmapped_mem);
stderr->_flags2 = old_flags2;
_IO_funlockfile (stderr);
}
--
2.40.1
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH v2] malloc_stats(): Fix `unsigned int` overflow
2023-11-13 18:27 ` [PATCH v2] " Niklas Hambüchen
@ 2023-11-13 20:25 ` DJ Delorie
2023-11-13 23:10 ` Niklas Hambüchen
0 siblings, 1 reply; 10+ messages in thread
From: DJ Delorie @ 2023-11-13 20:25 UTC (permalink / raw)
To: Niklas Hambüchen; +Cc: libc-alpha, schwab
Niklas Hambchen <mail@nh2.me> writes:
> @@ -5374,7 +5374,7 @@ __malloc_stats (void)
> {
> int i;
> mstate ar_ptr;
> - unsigned int in_use_b = mp_.mmapped_mem, system_b = in_use_b;
> + size_t in_use_b = mp_.mmapped_mem, system_b = in_use_b;
Ok.
> @@ -5389,8 +5389,8 @@ __malloc_stats (void)
> __libc_lock_lock (ar_ptr->mutex);
> int_mallinfo (ar_ptr, &mi);
> fprintf (stderr, "Arena %d:\n", i);
> - fprintf (stderr, "system bytes = %10u\n", (unsigned int) mi.arena);
> - fprintf (stderr, "in use bytes = %10u\n", (unsigned int) mi.uordblks);
> + fprintf (stderr, "system bytes = %10zu\n", mi.arena);
> + fprintf (stderr, "in use bytes = %10zu\n", mi.uordblks);
Ok.
> - fprintf (stderr, "system bytes = %10u\n", system_b);
> - fprintf (stderr, "in use bytes = %10u\n", in_use_b);
> - fprintf (stderr, "max mmap bytes = %10lu\n",
> - (unsigned long) mp_.max_mmapped_mem);
> + fprintf (stderr, "system bytes = %10zu\n", system_b);
> + fprintf (stderr, "in use bytes = %10zu\n", in_use_b);
> + fprintf (stderr, "max mmap bytes = %10zu\n", mp_.max_mmapped_mem);
This needs a cast to (size_t) as max_mmapped_mem is INTERNAL_SIZE_T,
which may be smaller than size_t.
> - fprintf (stderr, "max mmap regions = %10u\n", (unsigned int) mp_.max_n_mmaps);
> + fprintf (stderr, "max mmap regions = %10d\n", mp_.max_n_mmaps);
This causes a negative number to be printed when max_n_mmaps increments
past 2^31, where using "u" defers bad results until 2^32. So IMHO this
one is a regression, not a fix.
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH v2] malloc_stats(): Fix `unsigned int` overflow
2023-11-13 20:25 ` DJ Delorie
@ 2023-11-13 23:10 ` Niklas Hambüchen
2023-11-13 23:23 ` DJ Delorie
0 siblings, 1 reply; 10+ messages in thread
From: Niklas Hambüchen @ 2023-11-13 23:10 UTC (permalink / raw)
To: DJ Delorie; +Cc: libc-alpha, schwab
> This needs a cast to (size_t) as max_mmapped_mem is INTERNAL_SIZE_T,
> which may be smaller than size_t.
Thanks, will fix!
>> + fprintf (stderr, "max mmap regions = %10d\n", mp_.max_n_mmaps);
>
> This causes a negative number to be printed when max_n_mmaps increments
> past 2^31, where using "u" defers bad results until 2^32. So IMHO this
> one is a regression, not a fix.
I'm not sure I understand:
That statement holds for all `int`s, so following this logic, all `int`s should be casted to `unsigned int` first and printed with `%u`, and `%d` would be quite useless.
Doesn't it make more sense to print an `int` with `%d` as normal, so that you can _see_ in `malloc_stats()` when it overflows?
The non-`malloc_stats()` code that uses the `int` will likely also behave strangely if this overflow happens, so it seems weird to pretend the value is of a different type in the malloc-internals inspection function.
(Besides, `max_n_mmaps` sounds like a count of mmaps, not a byte count, so it should be much less likely to overflow.)
Thanks!
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH v2] malloc_stats(): Fix `unsigned int` overflow
2023-11-13 23:10 ` Niklas Hambüchen
@ 2023-11-13 23:23 ` DJ Delorie
0 siblings, 0 replies; 10+ messages in thread
From: DJ Delorie @ 2023-11-13 23:23 UTC (permalink / raw)
To: Niklas Hambüchen; +Cc: libc-alpha, schwab
Niklas Hambchen <mail@nh2.me> writes:
>>> + fprintf (stderr, "max mmap regions = %10d\n", mp_.max_n_mmaps);
>>
>> This causes a negative number to be printed when max_n_mmaps increments
>> past 2^31, where using "u" defers bad results until 2^32. So IMHO this
>> one is a regression, not a fix.
>
> I'm not sure I understand:
> That statement holds for all `int`s, so following this logic, all
> `int`s should be casted to `unsigned int` first and printed with `%u`,
> and `%d` would be quite useless.
>
> Doesn't it make more sense to print an `int` with `%d` as normal, so
> that you can _see_ in `malloc_stats()` when it overflows?
It only really overflows when it wraps around 2^32. Until then, the
value is still useful, as long as you present it properly.
An alternative would be to print out "(overflowed)" if the value exceeds 2^31
It just didn't seem right to take something that prints 0..2^32-1 and
reduce it to only print 0..2^31-1.
The other cases were stored as size_t and potentially truncated, which
is a different sort of overflow bug.
^ permalink raw reply [flat|nested] 10+ messages in thread
end of thread, other threads:[~2023-11-13 23:23 UTC | newest]
Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed)
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2021-10-29 17:11 [PATCH] malloc_stats(): Fix `unsigned int` overflow Niklas Hambüchen
2021-10-29 19:50 ` DJ Delorie
2021-10-30 0:36 ` Niklas Hambüchen
2021-10-30 1:39 ` Siddhesh Poyarekar
2021-10-30 6:55 ` Andreas Schwab
2023-11-13 18:27 ` [PATCH v2] " Niklas Hambüchen
2023-11-13 20:25 ` DJ Delorie
2023-11-13 23:10 ` Niklas Hambüchen
2023-11-13 23:23 ` DJ Delorie
2021-11-01 12:34 ` [PATCH] " Adhemerval Zanella
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