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authorAl Viro <viro@ZenIV.linux.org.uk>2012-06-09 08:15:16 +0100
committerJames Morris <james.l.morris@oracle.com>2012-07-30 15:36:50 +1000
commite3fea3f70fd68af0574a5f24246cdb4ed07f2b74 (patch)
treec3a8ae06734b2987646dd89c87c0a16ee50d420e /security
parent5935e6dcaaa8f666dd7f1169fa87d36752ebeb94 (diff)
downloadlinux-e3fea3f70fd68af0574a5f24246cdb4ed07f2b74.tar.gz
selinux: fix selinux_inode_setxattr oops
OK, what we have so far is e.g. setxattr(path, name, whatever, 0, XATTR_REPLACE) with name being good enough to get through xattr_permission(). Then we reach security_inode_setxattr() with the desired value and size. Aha. name should begin with "security.selinux", or we won't get that far in selinux_inode_setxattr(). Suppose we got there and have enough permissions to relabel that sucker. We call security_context_to_sid() with value == NULL, size == 0. OK, we want ss_initialized to be non-zero. I.e. after everything had been set up and running. No problem... We do 1-byte kmalloc(), zero-length memcpy() (which doesn't oops, even thought the source is NULL) and put a NUL there. I.e. form an empty string. string_to_context_struct() is called and looks for the first ':' in there. Not found, -EINVAL we get. OK, security_context_to_sid_core() has rc == -EINVAL, force == 0, so it silently returns -EINVAL. All it takes now is not having CAP_MAC_ADMIN and we are fucked. All right, it might be a different bug (modulo strange code quoted in the report), but it's real. Easily fixed, AFAICS: Deal with size == 0, value == NULL case in selinux_inode_setxattr() Cc: stable@vger.kernel.org Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Tested-by: Dave Jones <davej@redhat.com> Reported-by: Dave Jones <davej@redhat.com> Signed-off-by: James Morris <james.l.morris@oracle.com>
Diffstat (limited to 'security')
-rw-r--r--security/selinux/hooks.c15
1 files changed, 10 insertions, 5 deletions
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 94c45a1531a..79690f401a5 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2791,11 +2791,16 @@ static int selinux_inode_setxattr(struct dentry *dentry, const char *name,
/* We strip a nul only if it is at the end, otherwise the
* context contains a nul and we should audit that */
- str = value;
- if (str[size - 1] == '\0')
- audit_size = size - 1;
- else
- audit_size = size;
+ if (value) {
+ str = value;
+ if (str[size - 1] == '\0')
+ audit_size = size - 1;
+ else
+ audit_size = size;
+ } else {
+ str = "";
+ audit_size = 0;
+ }
ab = audit_log_start(current->audit_context, GFP_ATOMIC, AUDIT_SELINUX_ERR);
audit_log_format(ab, "op=setxattr invalid_context=");
audit_log_n_untrustedstring(ab, value, audit_size);