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libc/shmfs: Ensure uniqueness of memfd.

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Use mktemp to create unique path for memfd, so other thread can't find file by path.

If don't do this, error will ocurr in this case:

thread 1:                             thread2:
open() -- refs = 1
					open() -- refs = 2
					unlink()
unlink()

thread1 and thread2 will map one buffer by using file path but not fd or address of buffer.

Signed-off-by: wangzhi16 <wangzhi16@xiaomi.com>
This commit is contained in:
wangzhi16
2025-05-22 19:36:29 +08:00
committed by GUIDINGLI
parent 01f7ff2bb7
commit abe70c37a2
1 changed files with 11 additions and 3 deletions
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libs/libc/misc/lib_memfd.c
+11 -3
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@@ -43,7 +43,7 @@
# define LIBC_MEM_FD_VFS_PATH CONFIG_LIBC_MEM_FD_VFS_PATH # define LIBC_MEM_FD_VFS_PATH CONFIG_LIBC_MEM_FD_VFS_PATH
#endif #endif
#define LIBC_MEM_FD_VFS_PATH_FMT LIBC_MEM_FD_VFS_PATH "/%s" #define LIBC_MEM_FD_VFS_PATH_FMT LIBC_MEM_FD_VFS_PATH "/%sXXXXXX"
/**************************************************************************** /****************************************************************************
* Public Functions * Public Functions
@@ -65,22 +65,30 @@ int memfd_create(FAR const char *name, unsigned int flags)
return -1; return -1;
} }
retry:
snprintf(path, PATH_MAX, LIBC_MEM_FD_VFS_PATH_FMT, name); snprintf(path, PATH_MAX, LIBC_MEM_FD_VFS_PATH_FMT, name);
mktemp(path);
# ifdef CONFIG_LIBC_MEMFD_SHMFS # ifdef CONFIG_LIBC_MEMFD_SHMFS
ret = shm_open(path, O_RDWR | flags, 0660); ret = shm_open(path, O_RDWR | O_EXCL | flags, 0660);
if (ret >= 0) if (ret >= 0)
{ {
shm_unlink(path); shm_unlink(path);
} }
# else # else
mkdir(LIBC_MEM_FD_VFS_PATH, 0666); mkdir(LIBC_MEM_FD_VFS_PATH, 0666);
ret = open(path, O_RDWR | flags, 0660); ret = open(path, O_RDWR | O_EXCL | flags, 0660);
if (ret >= 0) if (ret >= 0)
{ {
unlink(path); unlink(path);
} }
# endif # endif
if (ret < 0 && get_errno() == EEXIST)
{
goto retry;
}
lib_put_pathbuffer(path); lib_put_pathbuffer(path);
return ret; return ret;
#endif #endif