@@ -1288,8 +1288,7 @@ static int64_t get_file_align(int fd)
static int file_ram_open(const char *path,
const char *region_name,
bool readonly,
- bool *created,
- Error **errp)
+ bool *created)
{
char *filename;
char *sanitized_name;
@@ -1304,6 +1303,10 @@ static int file_ram_open(const char *path,
break;
}
if (errno == ENOENT) {
+ if (readonly) {
+ /* Refuse to create new, readonly files. */
+ return -ENOENT;
+ }
/* @path names a file that doesn't exist, create it */
fd = open(path, O_RDWR | O_CREAT | O_EXCL, 0644);
if (fd >= 0) {
@@ -1333,10 +1336,7 @@ static int file_ram_open(const char *path,
g_free(filename);
}
if (errno != EEXIST && errno != EINTR) {
- error_setg_errno(errp, errno,
- "can't open backing store %s for guest RAM",
- path);
- return -1;
+ return -errno;
}
/*
* Try again on EINTR and EEXIST. The latter happens when
@@ -1946,8 +1946,10 @@ RAMBlock *qemu_ram_alloc_from_file(ram_addr_t size, MemoryRegion *mr,
RAMBlock *block;
fd = file_ram_open(mem_path, memory_region_name(mr),
- !!(ram_flags & RAM_READONLY_FD), &created, errp);
+ !!(ram_flags & RAM_READONLY_FD), &created);
if (fd < 0) {
+ error_setg_errno(errp, -fd, "can't open backing store %s for guest RAM",
+ mem_path);
return NULL;
}
Currently, if a file does not exist yet, file_ram_open() will create new empty file and open it writable. However, it even does that when readonly=true was specified. Specifying O_RDONLY instead to create a new readonly file would theoretically work, however, ftruncate() will refuse to resize the new empty file and we'll get a warning: ftruncate: Invalid argument And later eventually more problems when actually mmap'ing that file and accessing it. If someone intends to let QEMU open+mmap a file read-only, better create+resize+fill that file ahead of time outside of QEMU context. We'll now fail with: ./qemu-system-x86_64 \ -object memory-backend-file,id=ram0,mem-path=tmp,readonly=true,size=1g qemu-system-x86_64: can't open backing store tmp for guest RAM: No such file or directory All use cases of readonly files (R/O NVDIMMs, VM templating) work on existing files, so silently creating new files might just hide user errors when accidentally specifying a non-existent file. Note that the only memory-backend-file will end up calling memory_region_init_ram_from_file() -> qemu_ram_alloc_from_file() -> file_ram_open(). Move error reporting to the single caller. Message-ID: <20230906120503.359863-7-david@redhat.com> Acked-by: Peter Xu <peterx@redhat.com> Signed-off-by: David Hildenbrand <david@redhat.com> --- softmmu/physmem.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-)