Messages in this thread | | | Date | Wed, 14 Feb 2018 19:12:03 +0200 | From | "Michael S. Tsirkin" <> | Subject | Re: [PATCH v14 9/9] RFC: fw_cfg: do DMA read operation |
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On Wed, Feb 14, 2018 at 06:08:48PM +0100, Marc-Andre Lureau wrote: > Hi > > On Wed, Feb 14, 2018 at 5:59 PM, Michael S. Tsirkin <mst@redhat.com> wrote: > > On Wed, Feb 14, 2018 at 05:52:10PM +0100, Marc-Andre Lureau wrote: > >> >> @@ -282,8 +320,9 @@ static int fw_cfg_do_platform_probe(struct platform_device *pdev) > >> >> #endif > >> >> > >> >> /* verify fw_cfg device signature */ > >> >> - fw_cfg_read_blob(FW_CFG_SIGNATURE, sig, 0, FW_CFG_SIG_SIZE); > >> >> - if (memcmp(sig, "QEMU", FW_CFG_SIG_SIZE) != 0) { > >> >> + if (fw_cfg_read_blob(FW_CFG_SIGNATURE, sig, > >> >> + 0, FW_CFG_SIG_SIZE, false) < 0 || > >> >> + memcmp(sig, "QEMU", FW_CFG_SIG_SIZE) != 0) { > >> >> fw_cfg_io_cleanup(); > >> >> return -ENODEV; > >> >> } > >> > > >> > Rather than add dead code, how about a promise not to > >> > fail if dma is disabled? Patch will be smaller then. > >> > >> Even with dma disabled, you could have a locking bug which was > >> silently ignored before and is now taken into account. > > > > I see. I'd start with a patch reporting errors to users then. > > That would be a bugfix and can be merged for this version. > > silently is the wrong word for it, there is already a WARN().
it's not visible to userspace though.
> However, > the memcmp was done on uninitialzed sig[] (which likely resulted in > returning -ENODEV in the function)
Oh, we have an access to an uninitialized memory too. Fun!
> Now it can check if the function failed to read before doing the memcmp. > > Hope that clarifies it.
I think I get it. I'd make it a bugfix patch as patch 7 in the series. (patch 1-6 are applied in my tree, will merge in this window if they do not blow up).
> > > >> > > >> >> @@ -466,8 +505,8 @@ static ssize_t fw_cfg_sysfs_read_raw(struct file *filp, struct kobject *kobj, > >> >> if (count > entry->size - pos) > >> >> count = entry->size - pos; > >> >> > >> >> - fw_cfg_read_blob(entry->select, buf, pos, count); > >> >> - return count; > >> >> + /* do not use DMA, virt_to_phys(buf) might not be ok */ > >> >> + return fw_cfg_read_blob(entry->select, buf, pos, count, false); > >> >> } > >> >> > >> >> static struct bin_attribute fw_cfg_sysfs_attr_raw = { > >> >> @@ -632,7 +671,12 @@ static int fw_cfg_register_dir_entries(void) > >> >> struct fw_cfg_file *dir; > >> >> size_t dir_size; > >> >> > >> >> - fw_cfg_read_blob(FW_CFG_FILE_DIR, &files.count, 0, sizeof(files.count)); > >> >> + ret = fw_cfg_read_blob(FW_CFG_FILE_DIR, &files.count, > >> >> + 0, sizeof(files.count), false); > >> >> + if (ret < 0) { > >> >> + return ret; > >> >> + } > >> >> + > >> >> count = be32_to_cpu(files.count); > >> >> dir_size = count * sizeof(struct fw_cfg_file); > >> >> > >> >> @@ -640,7 +684,11 @@ static int fw_cfg_register_dir_entries(void) > >> >> if (!dir) > >> >> return -ENOMEM; > >> >> > >> >> - fw_cfg_read_blob(FW_CFG_FILE_DIR, dir, sizeof(files.count), dir_size); > >> >> + ret = fw_cfg_read_blob(FW_CFG_FILE_DIR, dir, > >> >> + sizeof(files.count), dir_size, false); > >> >> + if (ret < 0) { > >> >> + goto end; > >> >> + } > >> >> > >> >> for (i = 0; i < count; i++) { > >> >> ret = fw_cfg_register_file(&dir[i]); > >> >> @@ -648,6 +696,7 @@ static int fw_cfg_register_dir_entries(void) > >> >> break; > >> >> } > >> >> > >> >> +end: > >> >> kfree(dir); > >> >> return ret; > >> >> } > >> >> @@ -688,7 +737,10 @@ static int fw_cfg_sysfs_probe(struct platform_device *pdev) > >> >> goto err_probe; > >> >> > >> >> /* get revision number, add matching top-level attribute */ > >> >> - fw_cfg_read_blob(FW_CFG_ID, &rev, 0, sizeof(rev)); > >> >> + err = fw_cfg_read_blob(FW_CFG_ID, &rev, 0, sizeof(rev), false); > >> >> + if (err < 0) { > >> >> + goto err_probe; > >> >> + } > >> >> fw_cfg_rev = le32_to_cpu(rev); > >> >> err = sysfs_create_file(fw_cfg_top_ko, &fw_cfg_rev_attr.attr); > >> >> if (err) > >> >> -- > >> >> 2.16.1.73.g5832b7e9f2
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