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spa: Bounds-check pointers before dereferencing them

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Add a new overflow-safe function to check if region p2 of size s2 fits
completely in p1 of size s1 and, if it does, return the amount of bytes
in p1 that come after the end of p2.  Use this to bounds check the pod
iterators while ensuring that the pointer is bounds checked before being
dereferenced.

The spa_pod*_next() functions can still create an out-of-bounds pointer,
but this will not be dereferenced.  Fixing this requires either
additional complexity in these functions or forbidding POD structs,
objects, and sequences that have a length that is not a multiple of 8
bytes.

Fixes: 92ac9a355f ("spa: add spa_ptrinside")
Signed-off-by: Demi Marie Obenour <demiobenour@gmail.com>
This commit is contained in:
Demi Marie Obenour 2023-12-21 14:17:53 -05:00 • committed by Wim Taymans
parent c130ec9de9
commit 0227a30bcf
2 changed files with 56 additions and 14 deletions
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51
spa/include/spa/utils/defs.h
View file

@ -9,17 +9,25 @@
extern "C" {
# if __cplusplus >= 201103L
# define SPA_STATIC_ASSERT_IMPL(expr, msg, ...) static_assert(expr, msg)
# define SPA_ALIGNOF alignof
# endif
#elif __STDC_VERSION__ >= 202311L
# define SPA_STATIC_ASSERT_IMPL(expr, msg, ...) static_assert(expr, msg)
# define SPA_ALIGNOF alignof
#else
# include <stdbool.h>
# if __STDC_VERSION__ >= 201112L
# define SPA_STATIC_ASSERT_IMPL(expr, msg, ...) _Static_assert(expr, msg)
# define SPA_ALIGNOF _Alignof
# endif
#endif
#ifndef SPA_STATIC_ASSERT_IMPL
#define SPA_STATIC_ASSERT_IMPL(expr, ...) \
((void)sizeof(struct { int spa_static_assertion_failed : 2 * !!(expr) - 1; }))
#endif
#ifndef SPA_ALIGNOF
#define SPA_ALIGNOF __alignof__
#endif
#define SPA_STATIC_ASSERT(expr, ...) SPA_STATIC_ASSERT_IMPL(expr, ## __VA_ARGS__, "`" #expr "` evaluated to false")
@ -191,15 +199,6 @@ struct spa_fraction {
#define SPA_PTRDIFF(p1,p2) ((intptr_t)(p1) - (intptr_t)(p2))
static inline bool spa_ptrinside(const void *p1, size_t s1, const void *p2, size_t s2)
{
return (uintptr_t)p1 <= (uintptr_t)p2 && s2 <= s1 &&
(uintptr_t)p2 - (uintptr_t)p1 <= s1 - s2;
}
#define SPA_PTR_TO_INT(p) ((int) ((intptr_t) (p)))
#define SPA_INT_TO_PTR(u) ((void*) ((intptr_t) (u)))
#define SPA_PTR_TO_UINT32(p) ((uint32_t) ((uintptr_t) (p)))
#define SPA_UINT32_TO_PTR(u) ((void*) ((uintptr_t) (u)))
@ -287,6 +286,40 @@ static inline bool spa_ptrinside(const void *p1, size_t s1, const void *p2, size
#endif
#endif
static inline bool spa_ptrinside(const void *p1, size_t s1, const void *p2, size_t s2,
size_t *remaining)
{
if (SPA_LIKELY((uintptr_t)p1 <= (uintptr_t)p2 && s2 <= s1 &&
(uintptr_t)p2 - (uintptr_t)p1 <= s1 - s2)) {
if (remaining != NULL)
*remaining = ((uintptr_t)p1 + s1) - ((uintptr_t)p2 + s2);
return true;
} else {
if (remaining != NULL)
*remaining = 0;
return false;
}
}
static inline bool spa_ptr_inside_and_aligned(const void *p1, size_t s1,
const void *p2, size_t s2, size_t align,
size_t *remaining)
{
if (SPA_IS_ALIGNED(p2, align)) {
return spa_ptrinside(p1, s1, p2, s2, remaining);
} else {
if (remaining != NULL)
*remaining = 0;
return false;
}
}
#define spa_ptr_type_inside(p1, s1, p2, type, remaining) \
spa_ptr_inside_and_aligned(p1, s1, p2, sizeof(type), SPA_ALIGNOF(type), remaining)
#define SPA_PTR_TO_INT(p) ((int) ((intptr_t) (p)))
#define SPA_INT_TO_PTR(u) ((void*) ((intptr_t) (u)))
#define SPA_STRINGIFY_1(...) #__VA_ARGS__
#define SPA_STRINGIFY(...) SPA_STRINGIFY_1(__VA_ARGS__)