On Fri, 2013-01-25 at 11:50 +0800, Lingzhu Xiang wrote: > On 01/25/2013 08:25 AM, Al Viro wrote: > > 1) process A does write() on efivars file, reaches ->get_variable(), > > gets newdatasize set, drops efivars->lock and loses CPU before an attempt to > > grab ->i_mutex. process B comes and does the same thing, replacing the > > variable contents. Then it grabs ->i_mutex, updates size, drops ->i_mutex > > and buggers off. At which point A gets CPU back and proceeds to set size > > to whatever would be valid for its write. Only the value is bogus now... > > There are a few other things that makes size bogus now. > > 1. truncate() never touches nvram but pretends to be changing size. Good catch. Looks like we need to provide an implementation for this. > 2. Empty files come back with non-zero size after remount. They are imported > from sysfs when mounting. Eeek. The return value of get_variable() isn't checked in efivarfs_fill_super(). > 3. Arguably reading empty files could just return empty instead of returning > EIO/EFI_NOT_FOUND from firmware. Yeah, I think Jeremy has a patch to fix this. > 4. EFI_VARIABLE_APPEND_WRITE with EFI_OUT_OF_RESOURCES truncates size but you > can still read its content. I'm not sure what you mean by this. Could you please explain? Thanks for the feedback. -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
