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Assume unsigned uid_t/gid_t #167

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Assume unsigned uid_t/gid_t #167

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36 changes: 22 additions & 14 deletions src/bindfs.c
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Original file line number Diff line number Diff line change
Expand Up @@ -110,10 +110,8 @@

#endif

/* We pessimistically assume signed uid_t and gid_t in our overflow checks,
mostly because supporting both cases would require a bunch more code. */
static const int64_t UID_T_MAX = ((1LL << (sizeof(uid_t)*8-1)) - 1);
static const int64_t GID_T_MAX = ((1LL << (sizeof(gid_t)*8-1)) - 1);
static const uint64_t UID_T_MAX = ((1ULL << (sizeof(uid_t)*8)) - 1);
static const uint64_t GID_T_MAX = ((1ULL << (sizeof(gid_t)*8)) - 1);
static const int UID_GID_OVERFLOW_ERRNO = EIO;

/* SETTINGS */
Expand Down Expand Up @@ -242,7 +240,8 @@ static bool apply_uid_offset(uid_t *uid);
static bool apply_gid_offset(gid_t *gid);
static bool unapply_uid_offset(uid_t *uid);
static bool unapply_gid_offset(gid_t *gid);
static bool bounded_add(int64_t* a, int64_t b, int64_t max);
static bool bounded_add(uint64_t* a, int64_t b, uint64_t max);
static bool bounded_sub(uint64_t* a, int64_t b, uint64_t max);

#ifdef __linux__
static size_t round_up_buffer_size_for_direct_io(size_t size);
Expand Down Expand Up @@ -634,7 +633,7 @@ static int delete_file(const char *path, int (*target_delete_func)(const char *)
}

static bool apply_uid_offset(uid_t *uid) {
int64_t value = (int64_t)*uid;
uint64_t value = (uint64_t)*uid;
if (bounded_add(&value, settings.uid_offset, UID_T_MAX)) {
*uid = (uid_t)value;
return true;
Expand All @@ -645,7 +644,7 @@ static bool apply_uid_offset(uid_t *uid) {
}

static bool apply_gid_offset(gid_t *gid) {
int64_t value = (int64_t)*gid;
uint64_t value = (uint64_t)*gid;
if (bounded_add(&value, settings.gid_offset, GID_T_MAX)) {
*gid = (uid_t)value;
return true;
Expand All @@ -656,8 +655,8 @@ static bool apply_gid_offset(gid_t *gid) {
}

static bool unapply_uid_offset(uid_t *uid) {
int64_t value = (int64_t)*uid;
if (bounded_add(&value, -settings.uid_offset, UID_T_MAX)) {
uint64_t value = (uint64_t)*uid;
if (bounded_sub(&value, settings.uid_offset, UID_T_MAX)) {
*uid = (uid_t)value;
return true;
} else {
Expand All @@ -667,8 +666,8 @@ static bool unapply_uid_offset(uid_t *uid) {
}

static bool unapply_gid_offset(gid_t *gid) {
int64_t value = (int64_t)*gid;
if (bounded_add(&value, -settings.gid_offset, GID_T_MAX)) {
uint64_t value = (uint64_t)*gid;
if (bounded_sub(&value, settings.gid_offset, GID_T_MAX)) {
*gid = (uid_t)value;
return true;
} else {
Expand All @@ -677,9 +676,18 @@ static bool unapply_gid_offset(gid_t *gid) {
}
}

static bool bounded_add(int64_t* a, int64_t b, int64_t max) {
int64_t result;
if (!__builtin_add_overflow(*a, b, &result) && 0 <= result && result <= max) {
static bool bounded_add(uint64_t* a, int64_t b, uint64_t max) {
uint64_t result;
if (!__builtin_add_overflow(*a, b, &result) && result <= max) {
*a = result;
return true;
}
return false;
}

static bool bounded_sub(uint64_t* a, int64_t b, uint64_t max) {
uint64_t result;
if (!__builtin_sub_overflow(*a, b, &result) && result <= max) {
*a = result;
return true;
}
Expand Down
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