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mmap-cache: check offset and size more carefully

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PAGE_ALIGN() and friends take size_t, while offset is uint64_t.
Let's use macros for uint64_t.

Also, mmap() takes size_t for size. So, let's also use size_t to
calculate a window size.

Prompted by CID#1491286.
This commit is contained in:
Yu Watanabe 2023-10-18 13:49:14 +09:00
parent ffee7b97e3
commit c886f2d26e
1 changed files with 20 additions and 20 deletions
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40
src/libsystemd/sd-journal/mmap-cache.c
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@ -71,7 +71,7 @@ struct MMapCache {
/* Tiny windows increase mmap activity and the chance of exposing unsafe use. */
# define WINDOW_SIZE (page_size())
#else
# define WINDOW_SIZE (8ULL*1024ULL*1024ULL)
# define WINDOW_SIZE ((size_t) (UINT64_C(8) * UINT64_C(1024) * UINT64_C(1024)))
#endif
MMapCache* mmap_cache_new(void) {
@ -269,7 +269,6 @@ static int add_mmap(
struct stat *st,
Window **ret) {
uint64_t woffset, wsize;
Window *w;
void *d;
int r;
@ -278,41 +277,42 @@ static int add_mmap(
assert(size > 0);
assert(ret);
woffset = offset & ~((uint64_t) page_size() - 1ULL);
wsize = size + (offset - woffset);
wsize = PAGE_ALIGN(wsize);
/* overflow check */
if (size > SIZE_MAX - PAGE_OFFSET_U64(offset))
return -EADDRNOTAVAIL;
if (wsize < WINDOW_SIZE) {
size = PAGE_ALIGN(size + PAGE_OFFSET_U64(offset));
offset = PAGE_ALIGN_DOWN_U64(offset);
if (size < WINDOW_SIZE) {
uint64_t delta;
delta = PAGE_ALIGN((WINDOW_SIZE - wsize) / 2);
if (delta > offset)
woffset = 0;
else
woffset -= delta;
wsize = WINDOW_SIZE;
delta = PAGE_ALIGN((WINDOW_SIZE - size) / 2);
offset = LESS_BY(offset, delta);
size = WINDOW_SIZE;
}
if (st) {
/* Memory maps that are larger then the files underneath have undefined behavior. Hence,
* clamp things to the file size if we know it */
if (woffset >= (uint64_t) st->st_size)
if (offset >= (uint64_t) st->st_size)
return -EADDRNOTAVAIL;
if (woffset + wsize > (uint64_t) st->st_size)
wsize = PAGE_ALIGN(st->st_size - woffset);
if (size > (uint64_t) st->st_size - offset)
size = PAGE_ALIGN((uint64_t) st->st_size - offset);
}
r = mmap_try_harder(f, NULL, MAP_SHARED, woffset, wsize, &d);
if (size >= SIZE_MAX)
return -EADDRNOTAVAIL;
r = mmap_try_harder(f, NULL, MAP_SHARED, offset, size, &d);
if (r < 0)
return r;
w = window_add(f, woffset, wsize, d);
w = window_add(f, offset, size, d);
if (!w) {
(void) munmap(d, wsize);
(void) munmap(d, size);
return -ENOMEM;
}