[PATCH] mem-pool: use st_add() in mem_pool_strvfmt()
- From
René Scharfe <l.s.r@web.de>
- Date
- Mar 31, 2024, 18:53 UTC
- Message-ID
- <bbe00b9e-64d8-4ec8-a2b9-2c6917c72dbd@web.de>
If len is INT_MAX in mem_pool_strvfmt(), then len + 1 overflows. Casting it to size_t would prevent that. Use st_add() to go a step further and make the addition *obviously* safe. The compiler can optimize the check away on platforms where SIZE_MAX > INT_MAX, i.e. basically everywhere.
Signed-off-by: René Scharfe <l.s.r@web.de> --- mem-pool.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/mem-pool.c b/mem-pool.c index 2078c22b09..3065b12b23 100644 --- a/mem-pool.c +++ b/mem-pool.c @@ -115,6 +115,7 @@ static char *mem_pool_strvfmt(struct mem_pool *pool, const char *fmt, size_t available = block ? block->end - block->next_free : 0; va_list cp; int len, len2; + size_t size; char *ret; va_copy(cp, ap); @@ -123,13 +124,14 @@ static char *mem_pool_strvfmt(struct mem_pool *pool, const char *fmt, if (len < 0) BUG("your vsnprintf is broken (returned %d)", len); - ret = mem_pool_alloc(pool, len + 1); /* 1 for NUL */ + size = st_add(len, 1); /* 1 for NUL */ + ret = mem_pool_alloc(pool, size); /* Shortcut; relies on mem_pool_alloc() not touching buffer contents. */ if (ret == next_free) return ret; - len2 = vsnprintf(ret, len + 1, fmt, ap); + len2 = vsnprintf(ret, size, fmt, ap); if (len2 != len) BUG("your vsnprintf is broken (returns inconsistent lengths)"); return ret; -- 2.44.0