commit 16554464bcd9d77b07c6ff419dc54f00e394fa50

Author: DJ Delorie <dj@redhat.com>

Date:   Tue Dec 3 17:44:36 2019 -0500

    Correct range checking in mallopt/mxfast/tcache [BZ #25194]

    do_set_tcache_max, do_set_mxfast:

    Fix two instances of comparing "size_t < 0"

    Both cases have upper limit, so the "negative value" case

    is already handled via overflow semantics.

    do_set_tcache_max, do_set_tcache_count:

    Fix return value on error.  Note: currently not used.

    mallopt:

    pass return value of helper functions to user.  Behavior should

    only be actually changed for mxfast, where we restore the old

    (pre-tunables) behavior.

    Reviewed-by: Carlos O'Donell <carlos@redhat.com>

diff --git a/malloc/malloc.c b/malloc/malloc.c

index 90825b2aaed53761..00a37f218c0ab3b2 100644

--- a/malloc/malloc.c

+++ b/malloc/malloc.c

@@ -5111,13 +5111,14 @@ static inline int

 __always_inline

 do_set_tcache_max (size_t value)

 {

-  if (value >= 0 && value <= MAX_TCACHE_SIZE)

+  if (value <= MAX_TCACHE_SIZE)

     {

       LIBC_PROBE (memory_tunable_tcache_max_bytes, 2, value, mp_.tcache_max_bytes);

       mp_.tcache_max_bytes = value;

       mp_.tcache_bins = csize2tidx (request2size(value)) + 1;

+      return 1;

     }

-  return 1;

+  return 0;

 }

 static inline int

@@ -5128,8 +5129,9 @@ do_set_tcache_count (size_t value)

     {

       LIBC_PROBE (memory_tunable_tcache_count, 2, value, mp_.tcache_count);

       mp_.tcache_count = value;

+      return 1;

     }

-  return 1;

+  return 0;

 }

 static inline int

@@ -5146,7 +5148,7 @@ static inline int

 __always_inline

 do_set_mxfast (size_t value)

 {

-  if (value >= 0 && value <= MAX_FAST_SIZE)

+  if (value <= MAX_FAST_SIZE)

     {

       LIBC_PROBE (memory_mallopt_mxfast, 2, value, get_max_fast ());

       set_max_fast (value);

@@ -5171,18 +5173,24 @@ __libc_mallopt (int param_number, int value)

      (see definition of set_max_fast).  */

   malloc_consolidate (av);

+  /* Many of these helper functions take a size_t.  We do not worry

+     about overflow here, because negative int values will wrap to

+     very large size_t values and the helpers have sufficient range

+     checking for such conversions.  Many of these helpers are also

+     used by the tunables macros in arena.c.  */

+

   switch (param_number)

     {

     case M_MXFAST:

-      do_set_mxfast (value);

+      res = do_set_mxfast (value);

       break;

     case M_TRIM_THRESHOLD:

-      do_set_trim_threshold (value);

+      res = do_set_trim_threshold (value);

       break;

     case M_TOP_PAD:

-      do_set_top_pad (value);

+      res = do_set_top_pad (value);

       break;

     case M_MMAP_THRESHOLD:

@@ -5190,25 +5198,25 @@ __libc_mallopt (int param_number, int value)

       break;

     case M_MMAP_MAX:

-      do_set_mmaps_max (value);

+      res = do_set_mmaps_max (value);

       break;

     case M_CHECK_ACTION:

-      do_set_mallopt_check (value);

+      res = do_set_mallopt_check (value);

       break;

     case M_PERTURB:

-      do_set_perturb_byte (value);

+      res = do_set_perturb_byte (value);

       break;

     case M_ARENA_TEST:

       if (value > 0)

-	do_set_arena_test (value);

+	res = do_set_arena_test (value);

       break;

     case M_ARENA_MAX:

       if (value > 0)

-	do_set_arena_max (value);

+	res = do_set_arena_max (value);

       break;

     }

   __libc_lock_unlock (av->mutex);