On Tue, Dec 19, 2023 at 4:09 AM Alfred Piccioni alpic@google.com wrote:
Some ioctl commands do not require ioctl permission, but are routed to other permissions such as FILE_GETATTR or FILE_SETATTR. This routing is done by comparing the ioctl cmd to a set of 64-bit flags (FS_IOC_*).
However, if a 32-bit process is running on a 64-bit kernel, it emits 32-bit flags (FS_IOC32_*) for certain ioctl operations. These flags are being checked erroneously, which leads to these ioctl operations being routed to the ioctl permission, rather than the correct file permissions.
This was also noted in a RED-PEN finding from a while back - "/* RED-PEN how should LSM module know it's handling 32bit? */".
This patch introduces a new hook, security_file_ioctl_compat, that is called from the compat ioctl syscall. All current LSMs have been changed to support this hook.
Reviewing the three places where we are currently using security_file_ioctl, it appears that only SELinux needs a dedicated compat change; TOMOYO and SMACK appear to be functional without any change.
Fixes: 0b24dcb7f2f7 ("Revert "selinux: simplify ioctl checking"") Signed-off-by: Alfred Piccioni alpic@google.com Cc: stable@vger.kernel.org
fs/ioctl.c | 3 +-- include/linux/lsm_hook_defs.h | 2 ++ include/linux/security.h | 7 +++++++ security/security.c | 17 +++++++++++++++++ security/selinux/hooks.c | 28 ++++++++++++++++++++++++++++ security/smack/smack_lsm.c | 1 + security/tomoyo/tomoyo.c | 1 + 7 files changed, 57 insertions(+), 2 deletions(-)
I made some minor style tweaks around line length and alignment, but otherwise this looked good to me. Thanks all!
While I agree this is definitely stable kernel material, given where we are at in the current kernel cycle, and with the end-of-year holidays in full swing, I'm going to merge this into lsm/dev and send it up to Linus during the next merge window. The stable tag will remain intact, so it will end up trickling down into the stable kernels, it will just take an extra week or so (which I think will be good from a testing perspective).