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| author | Wilco Dijkstra <wdijkstr@arm.com> | 2019-05-10 16:38:21 +0100 |
|---|---|---|
| committer | Wilco Dijkstra <wdijkstr@arm.com> | 2019-05-10 16:38:21 +0100 |
| commit | 5ad533e8e65092be962e414e0417112c65d154fb (patch) | |
| tree | bb926e04c328e70f54fc026cbee805c52d9b2f6d | |
| parent | 4aee85f96b881c1cb80a1fff752b8e2130a9a4d9 (diff) | |
| download | glibc-5ad533e8e65092be962e414e0417112c65d154fb.tar.gz glibc-5ad533e8e65092be962e414e0417112c65d154fb.tar.xz glibc-5ad533e8e65092be962e414e0417112c65d154fb.zip | |
Fix tcache count maximum (BZ #24531)
The tcache counts[] array is a char, which has a very small range and thus may overflow. When setting tcache_count tunable, there is no overflow check. However the tunable must not be larger than the maximum value of the tcache counts[] array, otherwise it can overflow when filling the tcache. [BZ #24531] * malloc/malloc.c (MAX_TCACHE_COUNT): New define. (do_set_tcache_count): Only update if count is small enough. * manual/tunables.texi (glibc.malloc.tcache_count): Document max value.
| -rw-r--r-- | ChangeLog | 7 | ||||
| -rw-r--r-- | malloc/malloc.c | 9 | ||||
| -rw-r--r-- | manual/tunables.texi | 4 |
3 files changed, 16 insertions, 4 deletions
diff --git a/ChangeLog b/ChangeLog index 185730361d..1ec840cf2b 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,10 @@ +2019-05-10 Wilco Dijkstra <wdijkstr@arm.com> + + [BZ #24531] + * malloc/malloc.c (MAX_TCACHE_COUNT): New define. + (do_set_tcache_count): Only update if count is small enough. + * manual/tunables.texi (glibc.malloc.tcache_count): Document max value. + 2019-05-10 Florian Weimer <fweimer@redhat.com> * nptl/sem_close.c (struct walk_closure): Define. diff --git a/malloc/malloc.c b/malloc/malloc.c index 0e3d4dd516..b8baaa2706 100644 --- a/malloc/malloc.c +++ b/malloc/malloc.c @@ -2905,6 +2905,8 @@ typedef struct tcache_perthread_struct tcache_entry *entries[TCACHE_MAX_BINS]; } tcache_perthread_struct; +#define MAX_TCACHE_COUNT 127 /* Maximum value of counts[] entries. */ + static __thread bool tcache_shutting_down = false; static __thread tcache_perthread_struct *tcache = NULL; @@ -5098,8 +5100,11 @@ do_set_tcache_max (size_t value) static __always_inline int do_set_tcache_count (size_t value) { - LIBC_PROBE (memory_tunable_tcache_count, 2, value, mp_.tcache_count); - mp_.tcache_count = value; + if (value <= MAX_TCACHE_COUNT) + { + LIBC_PROBE (memory_tunable_tcache_count, 2, value, mp_.tcache_count); + mp_.tcache_count = value; + } return 1; } diff --git a/manual/tunables.texi b/manual/tunables.texi index 749cabff1b..ae638823a2 100644 --- a/manual/tunables.texi +++ b/manual/tunables.texi @@ -189,8 +189,8 @@ per-thread cache. The default (and maximum) value is 1032 bytes on @deftp Tunable glibc.malloc.tcache_count The maximum number of chunks of each size to cache. The default is 7. -There is no upper limit, other than available system memory. If set -to zero, the per-thread cache is effectively disabled. +The upper limit is 127. If set to zero, the per-thread cache is effectively +disabled. The approximate maximum overhead of the per-thread cache is thus equal to the number of bins times the chunk count in each bin times the size |