diff --git a/block/raw-posix.c b/block/raw-posix.c index 8b6b92608bf9edb629109410f50e32c80ac7004d..4dfdf985b0c5e6c1d5943fb948ede77d5e311123 100644 --- a/block/raw-posix.c +++ b/block/raw-posix.c @@ -1257,9 +1257,43 @@ static int hdev_probe_device(const char *filename) return 0; } +static int check_hdev_writable(BDRVRawState *s) +{ +#if defined(BLKROGET) + /* Linux block devices can be configured "read-only" using blockdev(8). + * This is independent of device node permissions and therefore open(2) + * with O_RDWR succeeds. Actual writes fail with EPERM. + * + * bdrv_open() is supposed to fail if the disk is read-only. Explicitly + * check for read-only block devices so that Linux block devices behave + * properly. + */ + struct stat st; + int readonly = 0; + + if (fstat(s->fd, &st)) { + return -errno; + } + + if (!S_ISBLK(st.st_mode)) { + return 0; + } + + if (ioctl(s->fd, BLKROGET, &readonly) < 0) { + return -errno; + } + + if (readonly) { + return -EACCES; + } +#endif /* defined(BLKROGET) */ + return 0; +} + static int hdev_open(BlockDriverState *bs, const char *filename, int flags) { BDRVRawState *s = bs->opaque; + int ret; #if defined(__APPLE__) && defined(__MACH__) if (strstart(filename, "/dev/cdrom", NULL)) { @@ -1300,7 +1334,20 @@ static int hdev_open(BlockDriverState *bs, const char *filename, int flags) } #endif - return raw_open_common(bs, filename, flags, 0); + ret = raw_open_common(bs, filename, flags, 0); + if (ret < 0) { + return ret; + } + + if (flags & BDRV_O_RDWR) { + ret = check_hdev_writable(s); + if (ret < 0) { + raw_close(bs); + return ret; + } + } + + return ret; } #if defined(__linux__)