[PATCH 3/4] linux-user: Fix shmat(NULL) for h != g

From: Ilya Leoshkevich <iii@linux.ibm.com>
To: "Richard Henderson" <richard.henderson@linaro.org>,
	"Laurent Vivier" <laurent@vivier.eu>,
	"Alex Bennée" <alex.bennee@linaro.org>
Cc: qemu-devel@nongnu.org, Ilya Leoshkevich <iii@linux.ibm.com>
Subject: [PATCH 3/4] linux-user: Fix shmat(NULL) for h != g
Date: Mon, 25 Mar 2024 16:07:40 +0100	[thread overview]
Message-ID: <20240325153313.526888-4-iii@linux.ibm.com> (raw)
In-Reply-To: <20240325153313.526888-1-iii@linux.ibm.com>

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")
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 linux-user/mmap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/linux-user/mmap.c b/linux-user/mmap.c
index e88faf1ab3d..681b6db1b67 100644
--- a/linux-user/mmap.c
+++ b/linux-user/mmap.c
@@ -1358,7 +1358,7 @@ 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);
-- 
2.44.0


