From: Ilya Leoshkevich <iii@linux.ibm.com>
Date: Mon, 25 Mar 2024 19:23:01 +0000 (+0100)
Subject: linux-user: Fix shmat(NULL) for h != g
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=fa527b44c2d65d48cc3c5ac018dc935cc286f5a9;p=qemu.git

linux-user: Fix shmat(NULL) for h != g

In the h != g && shmaddr == NULL && !reserved_va case, target_shmat()
incorrectly mmap()s the initial anonymous range with
MAP_FIXED_NOREPLACE, even though the earlier mmap_find_vma() has
already reserved the respective address range.

Fix by using MAP_FIXED when "mapped", which is set after
mmap_find_vma(), is true.

Fixes: 78bc8ed9a8f0 ("linux-user: Rewrite target_shmat")
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Message-Id: <20240325192436.561154-4-iii@linux.ibm.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---

diff --git a/linux-user/mmap.c b/linux-user/mmap.c
index 4505fd7376..be3b9a68eb 100644
--- a/linux-user/mmap.c
+++ b/linux-user/mmap.c
@@ -1354,7 +1354,7 @@ abi_ulong target_shmat(CPUArchState *cpu_env, int shmid,
         if (h_len != t_len) {
             int mmap_p = PROT_READ | (shmflg & SHM_RDONLY ? 0 : PROT_WRITE);
             int mmap_f = MAP_PRIVATE | MAP_ANONYMOUS
-                       | (reserved_va || (shmflg & SHM_REMAP)
+                       | (reserved_va || mapped || (shmflg & SHM_REMAP)
                           ? MAP_FIXED : MAP_FIXED_NOREPLACE);
 
             test = mmap(want, m_len, mmap_p, mmap_f, -1, 0);