On Fri, 2018-05-04 at 00:02 +0000, Luis R. Rodriguez wrote: > If you can add Andres Rodriguez <[email protected]>, and Greg to your Cc list > in the future patches that'd be appreciated. > > On Tue, May 01, 2018 at 09:48:18AM -0400, Mimi Zohar wrote: > > Add an LSM hook prior to allowing firmware sysfs fallback loading. > > > > Signed-off-by: Mimi Zohar <[email protected]> > > Cc: Luis R. Rodriguez <[email protected]> > > Cc: David Howells <[email protected]> > > Cc: Kees Cook <[email protected]> > > Cc: Matthew Garrett <[email protected]> > > --- > > drivers/base/firmware_loader/fallback.c | 7 +++++++ > > include/linux/fs.h | 1 + > > 2 files changed, 8 insertions(+) > > > > diff --git a/drivers/base/firmware_loader/fallback.c > > b/drivers/base/firmware_loader/fallback.c > > index 31b5015b59fe..23d2af30474e 100644 > > --- a/drivers/base/firmware_loader/fallback.c > > +++ b/drivers/base/firmware_loader/fallback.c > > @@ -651,6 +651,8 @@ static bool fw_force_sysfs_fallback(unsigned int > > opt_flags) > > > > static bool fw_run_sysfs_fallback(unsigned int opt_flags) > > { > > + int ret; > > + > > if (fw_fallback_config.ignore_sysfs_fallback) { > > pr_info_once("Ignoring firmware sysfs fallback due to sysctl > > knob\n"); > > return false; > > @@ -659,6 +661,11 @@ static bool fw_run_sysfs_fallback(unsigned int > > opt_flags) > > if ((opt_flags & FW_OPT_NOFALLBACK)) > > return false; > > > > + /* Also permit LSMs and IMA to fail firmware sysfs fallback */ > > + ret = security_kernel_read_file(NULL, READING_FIRMWARE_FALLBACK); > > + if (ret < 0) > > + return ret; > > + > > return fw_force_sysfs_fallback(opt_flags); > > } > > > > diff --git a/include/linux/fs.h b/include/linux/fs.h > > index 760d8da1b6c7..dc16a73c3d38 100644 > > --- a/include/linux/fs.h > > +++ b/include/linux/fs.h > > @@ -2810,6 +2810,7 @@ extern int do_pipe_flags(int *, int); > > id(UNKNOWN, unknown) \ > > id(FIRMWARE, firmware) \ > > id(FIRMWARE_PREALLOC_BUFFER, firmware) \ > > + id(FIRMWARE_FALLBACK, firmware) \ > > If you're going to add this perhaps FIRMWARE_FALLBACK_SYSFS as we may later > get FIRMWARE_FALLBACK_EFI.
>From an IMA signature verification perspective, both are buffer based. The file signature is stored as a security xattr. Without a file descriptor, the kernel cannot verify the firmware signature. I don't have a problem with defining another enumeration. Perhaps other LSMs will want to be able to differentiate between sysfs and EFI fallback methods. Mimi
