diff options
author | Kees Cook <keescook@chromium.org> | 2020-10-02 20:38:20 +0300 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-10-05 14:37:03 +0300 |
commit | b64fcae74b6d6940d14243c963ab0089e8f0d82d (patch) | |
tree | 301791490a1bce0d017a380cc37475510ecee286 /include/linux/lsm_hooks.h | |
parent | 885352881f11f1f3113d8eb877786bcb6d720544 (diff) | |
download | linux-b64fcae74b6d6940d14243c963ab0089e8f0d82d.tar.xz |
LSM: Introduce kernel_post_load_data() hook
There are a few places in the kernel where LSMs would like to have
visibility into the contents of a kernel buffer that has been loaded or
read. While security_kernel_post_read_file() (which includes the
buffer) exists as a pairing for security_kernel_read_file(), no such
hook exists to pair with security_kernel_load_data().
Earlier proposals for just using security_kernel_post_read_file() with a
NULL file argument were rejected (i.e. "file" should always be valid for
the security_..._file hooks, but it appears at least one case was
left in the kernel during earlier refactoring. (This will be fixed in
a subsequent patch.)
Since not all cases of security_kernel_load_data() can have a single
contiguous buffer made available to the LSM hook (e.g. kexec image
segments are separately loaded), there needs to be a way for the LSM to
reason about its expectations of the hook coverage. In order to handle
this, add a "contents" argument to the "kernel_load_data" hook that
indicates if the newly added "kernel_post_load_data" hook will be called
with the full contents once loaded. That way, LSMs requiring full contents
can choose to unilaterally reject "kernel_load_data" with contents=false
(which is effectively the existing hook coverage), but when contents=true
they can allow it and later evaluate the "kernel_post_load_data" hook
once the buffer is loaded.
With this change, LSMs can gain coverage over non-file-backed data loads
(e.g. init_module(2) and firmware userspace helper), which will happen
in subsequent patches.
Additionally prepare IMA to start processing these cases.
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: KP Singh <kpsingh@google.com>
Link: https://lore.kernel.org/r/20201002173828.2099543-9-keescook@chromium.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include/linux/lsm_hooks.h')
-rw-r--r-- | include/linux/lsm_hooks.h | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index 9e2e3e63719d..6bb4f1a0158c 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -635,7 +635,17 @@ * @kernel_load_data: * Load data provided by userspace. * @id kernel load data identifier + * @contents if a subsequent @kernel_post_load_data will be called. * Return 0 if permission is granted. + * @kernel_post_load_data: + * Load data provided by a non-file source (usually userspace buffer). + * @buf pointer to buffer containing the data contents. + * @size length of the data contents. + * @id kernel load data identifier + * @description a text description of what was loaded, @id-specific + * Return 0 if permission is granted. + * This must be paired with a prior @kernel_load_data call that had + * @contents set to true. * @kernel_read_file: * Read a file specified by userspace. * @file contains the file structure pointing to the file being read |