diff options
authorEric W. Biederman <>2020-05-25 12:56:15 -0500
committerEric W. Biederman <>2020-05-26 13:11:00 -0500
commita4ae32c71fe90794127b32d26d7ad795813b502e (patch)
parent6a8b55ed4056ea5559ebe4f6a4b247f627870d4c (diff)
exec: Always set cap_ambient in cap_bprm_set_creds
An invariant of cap_bprm_set_creds is that every field in the new cred structure that cap_bprm_set_creds might set, needs to be set every time to ensure the fields does not get a stale value. The field cap_ambient is not set every time cap_bprm_set_creds is called, which means that if there is a suid or sgid script with an interpreter that has neither the suid nor the sgid bits set the interpreter should be able to accept ambient credentials. Unfortuantely because cap_ambient is not reset to it's original value the interpreter can not accept ambient credentials. Given that the ambient capability set is expected to be controlled by the caller, I don't think this is particularly serious. But it is definitely worth fixing so the code works correctly. I have tested to verify my reading of the code is correct and the interpreter of a sgid can receive ambient capabilities with this change and cannot receive ambient capabilities without this change. Cc: Cc: Andy Lutomirski <> Fixes: 58319057b784 ("capabilities: ambient capabilities") Signed-off-by: "Eric W. Biederman" <>
1 files changed, 1 insertions, 0 deletions
diff --git a/security/commoncap.c b/security/commoncap.c
index f4ee0ae106b2..0ca31c8bc0b1 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -812,6 +812,7 @@ int cap_bprm_set_creds(struct linux_binprm *bprm)
int ret;
kuid_t root_uid;
+ new->cap_ambient = old->cap_ambient;
if (WARN_ON(!cap_ambient_invariant_ok(old)))
return -EPERM;