| Message ID | 1500416736-49829-11-git-send-email-keescook@chromium.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Tue, Jul 18, 2017 at 3:25 PM, Kees Cook <keescook@chromium.org> wrote: > The examination of "current" to decide dumpability is wrong. This was a > check of and euid/uid (or egid/gid) mismatch in the existing process, > not the newly created one. This appears to stretch back into even the > "history.git" tree. Luckily, dumpability is later set in commit_creds(). > In earlier kernel versions before creds existed, similar checks also > existed late in the exec flow, covering up the mistake as far back as I > could find. > > Note that because the commit_creds() check examines differences of euid, > uid, egid, gid, and capabilities between the old and new creds, it would > look like the setup_new_exec() dumpability test could be entirely removed. > However, the secureexec test may cover a different set of tests (specific > to the LSMs) than what commit_creds() checks for. So, fix this test to > use secureexec (the removed euid tests are redundant to the commoncap > secureexec checks now). > > Cc: David Howells <dhowells@redhat.com> > Signed-off-by: Kees Cook <keescook@chromium.org> David (or anyone else), how does this (and the following undiscussed patches) look? I only have a few unreviewed patches in this series, and I'd like to get some more eyes on it. Thanks! -Kees > --- > fs/exec.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/exec.c b/fs/exec.c > index f9480d3e0b82..5241c8f25f5d 100644 > --- a/fs/exec.c > +++ b/fs/exec.c > @@ -1353,7 +1353,7 @@ void setup_new_exec(struct linux_binprm * bprm) > > current->sas_ss_sp = current->sas_ss_size = 0; > > - if (uid_eq(current_euid(), current_uid()) && gid_eq(current_egid(), current_gid())) > + if (!bprm->secureexec) > set_dumpable(current->mm, SUID_DUMP_USER); > else > set_dumpable(current->mm, suid_dumpable); > -- > 2.7.4 >
diff --git a/fs/exec.c b/fs/exec.c index f9480d3e0b82..5241c8f25f5d 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1353,7 +1353,7 @@ void setup_new_exec(struct linux_binprm * bprm) current->sas_ss_sp = current->sas_ss_size = 0; - if (uid_eq(current_euid(), current_uid()) && gid_eq(current_egid(), current_gid())) + if (!bprm->secureexec) set_dumpable(current->mm, SUID_DUMP_USER); else set_dumpable(current->mm, suid_dumpable);
The examination of "current" to decide dumpability is wrong. This was a check of and euid/uid (or egid/gid) mismatch in the existing process, not the newly created one. This appears to stretch back into even the "history.git" tree. Luckily, dumpability is later set in commit_creds(). In earlier kernel versions before creds existed, similar checks also existed late in the exec flow, covering up the mistake as far back as I could find. Note that because the commit_creds() check examines differences of euid, uid, egid, gid, and capabilities between the old and new creds, it would look like the setup_new_exec() dumpability test could be entirely removed. However, the secureexec test may cover a different set of tests (specific to the LSMs) than what commit_creds() checks for. So, fix this test to use secureexec (the removed euid tests are redundant to the commoncap secureexec checks now). Cc: David Howells <dhowells@redhat.com> Signed-off-by: Kees Cook <keescook@chromium.org> --- fs/exec.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)