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authorKees Cook <keescook@chromium.org>2022-10-26 16:31:11 -0700
committerKees Cook <keescook@chromium.org>2022-11-01 10:04:52 -0700
commit5a17f040fa332e71a45ca9ff02d6979d9176a423 (patch)
tree976a0250731074e8689c74665873f3b77f0b60c6 /drivers/base
parente9a40e1585d792751d3a122392695e5a53032809 (diff)
cred: Do not default to init_cred in prepare_kernel_cred()
A common exploit pattern for ROP attacks is to abuse prepare_kernel_cred() in order to construct escalated privileges[1]. Instead of providing a short-hand argument (NULL) to the "daemon" argument to indicate using init_cred as the base cred, require that "daemon" is always set to an actual task. Replace all existing callers that were passing NULL with &init_task. Future attacks will need to have sufficiently powerful read/write primitives to have found an appropriately privileged task and written it to the ROP stack as an argument to succeed, which is similarly difficult to the prior effort needed to escalate privileges before struct cred existed: locate the current cred and overwrite the uid member. This has the added benefit of meaning that prepare_kernel_cred() can no longer exceed the privileges of the init task, which may have changed from the original init_cred (e.g. dropping capabilities from the bounding set). [1] https://google.com/search?q=commit_creds(prepare_kernel_cred(0)) Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: David Howells <dhowells@redhat.com> Cc: "Rafael J. Wysocki" <rafael@kernel.org> Cc: Steve French <sfrench@samba.org> Cc: Ronnie Sahlberg <lsahlber@redhat.com> Cc: Shyam Prasad N <sprasad@microsoft.com> Cc: Tom Talpey <tom@talpey.com> Cc: Namjae Jeon <linkinjeon@kernel.org> Cc: Trond Myklebust <trond.myklebust@hammerspace.com> Cc: Anna Schumaker <anna@kernel.org> Cc: Chuck Lever <chuck.lever@oracle.com> Cc: Jeff Layton <jlayton@kernel.org> Cc: "David S. Miller" <davem@davemloft.net> Cc: Eric Dumazet <edumazet@google.com> Cc: Jakub Kicinski <kuba@kernel.org> Cc: Paolo Abeni <pabeni@redhat.com> Cc: "Michal Koutný" <mkoutny@suse.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: linux-cifs@vger.kernel.org Cc: samba-technical@lists.samba.org Cc: linux-nfs@vger.kernel.org Cc: netdev@vger.kernel.org Signed-off-by: Kees Cook <keescook@chromium.org> Acked-by: Luis Chamberlain <mcgrof@kernel.org> Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org> Acked-by: Russ Weight <russell.h.weight@intel.com> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Acked-by: Paulo Alcantara (SUSE) <pc@cjr.nz> Link: https://lore.kernel.org/r/20221026232943.never.775-kees@kernel.org
Diffstat (limited to 'drivers/base')
-rw-r--r--drivers/base/firmware_loader/main.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/base/firmware_loader/main.c b/drivers/base/firmware_loader/main.c
index 7c3590fd97c2..017c4cdb219e 100644
--- a/drivers/base/firmware_loader/main.c
+++ b/drivers/base/firmware_loader/main.c
@@ -821,7 +821,7 @@ _request_firmware(const struct firmware **firmware_p, const char *name,
* called by a driver when serving an unrelated request from userland, we use
* the kernel credentials to read the file.
*/
- kern_cred = prepare_kernel_cred(NULL);
+ kern_cred = prepare_kernel_cred(&init_task);
if (!kern_cred) {
ret = -ENOMEM;
goto out;