From 66018f59c0b29838ea628d828c8db4b28c873960 Mon Sep 17 00:00:00 2001 From: Ondrej Mosnacek Date: Thu, 3 Oct 2019 15:59:22 +0200 Subject: [PATCH] UPSTREAM: selinux: fix context string corruption in convert_context() string_to_context_struct() may garble the context string, so we need to copy back the contents again from the old context struct to avoid storing the corrupted context. Since string_to_context_struct() tokenizes (and therefore truncates) the context string and we are later potentially copying it with kstrdup(), this may eventually cause pieces of uninitialized kernel memory to be disclosed to userspace (when copying to userspace based on the stored length and not the null character). How to reproduce on Fedora and similar: # dnf install -y memcached # systemctl start memcached # semodule -d memcached # load_policy # load_policy # systemctl stop memcached # ausearch -m AVC type=AVC msg=audit(1570090572.648:313): avc: denied { signal } for pid=1 comm="systemd" scontext=system_u:system_r:init_t:s0 tcontext=system_u:object_r:unlabeled_t:s0 tclass=process permissive=0 trawcon=73797374656D5F75007400000000000070BE6E847296FFFF726F6D000096FFFF76 Cc: stable@vger.kernel.org Reported-by: Milos Malik Fixes: ee1a84fdfeed ("selinux: overhaul sidtab to fix bug and improve performance") Signed-off-by: Ondrej Mosnacek Acked-by: Stephen Smalley Signed-off-by: Paul Moore (cherry picked from commit 2a5243937c700ffe6a28e6557a4562a9ab0a17a4) Change-Id: I56add9632ba622b956adb00a2b1ecfc608a37c32 Bug: 140252993 Signed-off-by: Jeff Vander Stoep --- security/selinux/ss/services.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c index 82bd87278da0..5a2a4954a760 100644 --- a/security/selinux/ss/services.c +++ b/security/selinux/ss/services.c @@ -1934,7 +1934,14 @@ static int convert_context(struct context *oldc, struct context *newc, void *p) rc = string_to_context_struct(args->newp, NULL, s, newc, SECSID_NULL); if (rc == -EINVAL) { - /* Retain string representation for later mapping. */ + /* + * Retain string representation for later mapping. + * + * IMPORTANT: We need to copy the contents of oldc->str + * back into s again because string_to_context_struct() + * may have garbled it. + */ + memcpy(s, oldc->str, oldc->len); context_init(newc); newc->str = s; newc->len = oldc->len;