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Re: [PATCH 08/24] bsd-user: Use page_check_range_empty for MAP_EXCL


From: Warner Losh
Subject: Re: [PATCH 08/24] bsd-user: Use page_check_range_empty for MAP_EXCL
Date: Fri, 30 Jun 2023 12:46:37 -0600



On Fri, Jun 30, 2023 at 7:22 AM Richard Henderson <richard.henderson@linaro.org> wrote:
The previous check returned -1 when any page within
[start, start+len) is unmapped, not when all are unmapped.

Cc: Warner Losh <imp@bsdimp.com>
Cc: Kyle Evans <kevans@freebsd.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 bsd-user/mmap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/bsd-user/mmap.c b/bsd-user/mmap.c
index 565b9f97ed..07b5b8055e 100644
--- a/bsd-user/mmap.c
+++ b/bsd-user/mmap.c
@@ -609,7 +609,7 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int prot,
         }

         /* Reject the mapping if any page within the range is mapped */
-        if ((flags & MAP_EXCL) && page_check_range(start, len, 0) < 0) {
+        if ((flags & MAP_EXCL) && !page_check_range_empty(start, end - 1)) {

Won't computing end overflow if start is 1<<32 - len? Then subtracting one here would be too late. 

Warner

 
             errno = EINVAL;
             goto fail;
         }
--
2.34.1


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