With all "silently resizing" callers of ksize() refactored, remove the logic in ksize() that would allow it to be used to effectively change the size of an allocation (bypassing __alloc_size hints, etc). Users wanting this feature need to either use kmalloc_size_roundup() before an allocation, or call krealloc() directly.
For kfree_sensitive(), move the unpoisoning logic inline. Replace the open-coded ksize() in __do_krealloc with ksize() now that it doesn't perform unpoisoning. Cc: Christoph Lameter <[email protected]> Cc: Pekka Enberg <[email protected]> Cc: David Rientjes <[email protected]> Cc: Joonsoo Kim <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Vlastimil Babka <[email protected]> Cc: Roman Gushchin <[email protected]> Cc: Hyeonggon Yoo <[email protected]> Cc: Andrey Ryabinin <[email protected]> Cc: Alexander Potapenko <[email protected]> Cc: Andrey Konovalov <[email protected]> Cc: Dmitry Vyukov <[email protected]> Cc: Vincenzo Frascino <[email protected]> Cc: [email protected] Cc: [email protected] Signed-off-by: Kees Cook <[email protected]> --- mm/slab_common.c | 38 ++++++++++++++------------------------ 1 file changed, 14 insertions(+), 24 deletions(-) diff --git a/mm/slab_common.c b/mm/slab_common.c index d7420cf649f8..60b77bcdc2e3 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -1160,13 +1160,8 @@ __do_krealloc(const void *p, size_t new_size, gfp_t flags) void *ret; size_t ks; - /* Don't use instrumented ksize to allow precise KASAN poisoning. */ - if (likely(!ZERO_OR_NULL_PTR(p))) { - if (!kasan_check_byte(p)) - return NULL; - ks = kfence_ksize(p) ?: __ksize(p); - } else - ks = 0; + /* How large is the allocation actually? */ + ks = ksize(p); /* If the object still fits, repoison it precisely. */ if (ks >= new_size) { @@ -1232,8 +1227,10 @@ void kfree_sensitive(const void *p) void *mem = (void *)p; ks = ksize(mem); - if (ks) + if (ks) { + kasan_unpoison_range(mem, ks); memzero_explicit(mem, ks); + } kfree(mem); } EXPORT_SYMBOL(kfree_sensitive); @@ -1242,10 +1239,11 @@ EXPORT_SYMBOL(kfree_sensitive); * ksize - get the actual amount of memory allocated for a given object * @objp: Pointer to the object * - * kmalloc may internally round up allocations and return more memory + * kmalloc() may internally round up allocations and return more memory * than requested. ksize() can be used to determine the actual amount of - * memory allocated. The caller may use this additional memory, even though - * a smaller amount of memory was initially specified with the kmalloc call. + * allocated memory. The caller may NOT use this additional memory, unless + * it calls krealloc(). To avoid an alloc/realloc cycle, callers can use + * kmalloc_size_roundup() to find the size of the associated kmalloc bucket. * The caller must guarantee that objp points to a valid object previously * allocated with either kmalloc() or kmem_cache_alloc(). The object * must not be freed during the duration of the call. @@ -1254,13 +1252,11 @@ EXPORT_SYMBOL(kfree_sensitive); */ size_t ksize(const void *objp) { - size_t size; - /* - * We need to first check that the pointer to the object is valid, and - * only then unpoison the memory. The report printed from ksize() is - * more useful, then when it's printed later when the behaviour could - * be undefined due to a potential use-after-free or double-free. + * We need to first check that the pointer to the object is valid. + * The KASAN report printed from ksize() is more useful, then when + * it's printed later when the behaviour could be undefined due to + * a potential use-after-free or double-free. * * We use kasan_check_byte(), which is supported for the hardware * tag-based KASAN mode, unlike kasan_check_read/write(). @@ -1274,13 +1270,7 @@ size_t ksize(const void *objp) if (unlikely(ZERO_OR_NULL_PTR(objp)) || !kasan_check_byte(objp)) return 0; - size = kfence_ksize(objp) ?: __ksize(objp); - /* - * We assume that ksize callers could use whole allocated area, - * so we need to unpoison this area. - */ - kasan_unpoison_range(objp, size); - return size; + return kfence_ksize(objp) ?: __ksize(objp); } EXPORT_SYMBOL(ksize); -- 2.34.1 _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
