Re: [PATCH 0/5] selinux: minor cleanup suggestions

From: Stephen Smalley
Date: Tue Sep 29 2015 - 14:00:54 EST

On 09/25/2015 06:34 PM, Rasmus Villemoes wrote:
A few random things I stumbled on.

While I'm pretty sure of the change in 1/5, I'm also confused, because
the doc for the reverse security_sid_to_context state that
@scontext_len is set to "the length of the string", which one would
normally interpret as being what strlen() would give (i.e., without
the \0). However, security_sid_to_context_core clearly includes the \0
in the return value, and I think callers rely on that.

It is historical; originally security_context_to_sid() required @scontext to be NUL-terminated and @scontext_len to include the NUL byte in the length, and security_sid_to_context() returned a NUL-terminated @scontext and included the NUL byte in the returned length. However, when we switched SELinux to using xattrs rather than its own persistent label mapping, security_context_to_sid() was changed to accept contexts that did not already include the NUL because setfattr did not consider the NUL to be part of the attribute value for strings. So presently it accepts either form, although we prefer them to be NUL-terminated and canonicalize them to that form before returning to userspace.

Rasmus Villemoes (5):
selinux: introduce security_context_str_to_sid
selinux: remove pointless cast in selinux_inode_setsecurity()
selinux: use kmemdup in security_sid_to_context_core()
selinux: use kstrdup() in security_get_bools()
selinux: use sprintf return value

security/selinux/hooks.c | 14 +++++---------
security/selinux/include/security.h | 2 ++
security/selinux/selinuxfs.c | 26 +++++++++-----------------
security/selinux/ss/services.c | 22 +++++++++-------------
4 files changed, 25 insertions(+), 39 deletions(-)

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