Re: [Libguestfs] [libnbd PATCH 3/3] api: Add new API nbd_set_pread_initialize()

On Thu, Feb 10, 2022 at 09:38:30AM +0000, Richard W.M. Jones wrote: > On Wed, Feb 09, 2022 at 04:07:26PM -0600, Eric Blake wrote: > > + "set_pread_initialize", { > > + default_call with > > + args = [Bool "request"]; ret = RErr; > > + shortdesc = "control whether libnbd pre-initializes read buffers"; > > + longdesc = "\ > > +By default, libnbd will pre-initialize the contents of a buffer > > +passed to calls such as L<nbd_pread(3)> to all zeroes prior to checking > > +for any other errors, so that even if a client application passed in an > > +uninitialized buffer but fails to check for errors, it will not result > > +in a potential security risk caused by an accidental leak of prior heap > > +contents. However, for a client application that has audited that an > > +uninitialized buffer is never dereferenced, or which performs its own > > +pre-initialization, libnbd's sanitization efforts merely pessimize > > +performance. > > + > > +Calling this function with C<request> set to false tells libnbd to > > +skip the buffer initialization step in read commands."; > > + see_also = [Link "get_pread_initialize"; > > + Link "set_strict_mode"; > > + Link "pread"; Link "pread_structured"; Link "aio_pread"; > > + Link "aio_pread_structured"]; > > + }; > > Could it be worth mentioning CVE-2022-0485 by name in the text here? > And/or linking to: > https://listman.redhat.com/archives/libguestfs/2022-February/msg00104.html Good idea, I went with: diff --git i/generator/API.ml w/generator/API.ml index 9b7eb545..aaba9951 100644 --- i/generator/API.ml +++ w/generator/API.ml @@ -784,14 +784,19 @@ "set_pread_initialize", { shortdesc = "control whether libnbd pre-initializes read buffers"; longdesc = "\ By default, libnbd will pre-initialize the contents of a buffer -passed to calls such as L<nbd_pread(3)> to all zeroes prior to checking -for any other errors, so that even if a client application passed in an -uninitialized buffer but fails to check for errors, it will not result -in a potential security risk caused by an accidental leak of prior heap -contents. However, for a client application that has audited that an -uninitialized buffer is never dereferenced, or which performs its own -pre-initialization, libnbd's sanitization efforts merely pessimize -performance. +passed to calls such as L<nbd_pread(3)> to all zeroes prior to +checking for any other errors, so that even if a client application +passed in an uninitialized buffer but fails to check for errors, it +will not result in a potential security risk caused by an accidental +leak of prior heap contents (see CVE-2022-0485 in +L<libnbd-security(3)> for an example of a security hole in an +application built against an earlier version of libnbd that lacked +consistent pre-initialization). However, for a client application +that has audited that an uninitialized buffer is never dereferenced, +or which performs its own pre-initialization, libnbd's sanitization +efforts merely pessimize performance (although the time spent in +pre-initialization may pale in comparison to time spent waiting on +network packets). Calling this function with C<request> set to false tells libnbd to skip the buffer initialization step in read commands."; > > Anyway the whole patch series looks good, so: > > Reviewed-by: Richard W.M. Jones <rjones(a)redhat.com&gt; Series is now checked in with amendments, as ab52914b..e0953cb7