From: Paul Moore paul@paul-moore.com
This patch has been added to the 4.1 stable tree. If you have any objections, please let us know.
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[ Upstream commit ef28df55ac27e1e5cd122e19fa311d886d47a756 ]
The syzbot/syzkaller automated tests found a problem in security_context_to_sid_core() during early boot (before we load the SELinux policy) where we could potentially feed context strings without NUL terminators into the strcmp() function.
We already guard against this during normal operation (after the SELinux policy has been loaded) by making a copy of the context strings and explicitly adding a NUL terminator to the end. The patch extends this protection to the early boot case (no loaded policy) by moving the context copy earlier in security_context_to_sid_core().
Reported-by: syzbot syzkaller@googlegroups.com Signed-off-by: Paul Moore paul@paul-moore.com Reviewed-By: William Roberts william.c.roberts@intel.com Signed-off-by: Sasha Levin alexander.levin@microsoft.com --- security/selinux/ss/services.c | 18 ++++++++---------- 1 file changed, 8 insertions(+), 10 deletions(-)
diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c index 9e2d82070915..3308a8215180 100644 --- a/security/selinux/ss/services.c +++ b/security/selinux/ss/services.c @@ -1236,27 +1236,25 @@ static int security_context_to_sid_core(const char *scontext, u32 scontext_len, if (!scontext_len) return -EINVAL;
+ /* Copy the string to allow changes and ensure a NUL terminator */ + scontext2 = kmemdup_nul(scontext, scontext_len, gfp_flags); + if (!scontext2) + return -ENOMEM; + if (!ss_initialized) { int i;
for (i = 1; i < SECINITSID_NUM; i++) { - if (!strcmp(initial_sid_to_string[i], scontext)) { + if (!strcmp(initial_sid_to_string[i], scontext2)) { *sid = i; - return 0; + goto out; } } *sid = SECINITSID_KERNEL; - return 0; + goto out; } *sid = SECSID_NULL;
- /* Copy the string so that we can modify the copy as we parse it. */ - scontext2 = kmalloc(scontext_len + 1, gfp_flags); - if (!scontext2) - return -ENOMEM; - memcpy(scontext2, scontext, scontext_len); - scontext2[scontext_len] = 0; - if (force) { /* Save another copy for storing in uninterpreted form */ rc = -ENOMEM;