From c6b962ba0e84d84cb8434aae62108b537de04c2c Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Jos=C3=A9=20Bollo?= Date: Thu, 3 Apr 2014 13:48:41 +0200 Subject: [PATCH 28/54] SMACK: Fix handling value==NULL in post setxattr MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The function `smack_inode_post_setxattr` is called each time that a setxattr is done, for any value of name. The kernel allow to put value==NULL when size==0 to set an empty attribute value. The systematic call to smk_import_entry was causing the dereference of a NULL pointer hence a KERNEL PANIC! The problem can be produced easily by issuing the command `setfattr -n user.data file` under bash prompt when SMACK is active. Moving the call to smk_import_entry as proposed by this patch is correcting the behaviour because the function smack_inode_post_setxattr is called for the SMACK's attributes only if the function smack_inode_setxattr validated the value and its size (what will not be the case when size==0). It also has a benefical effect to not fill the smack hash with garbage values coming from any extended attribute write. Change-Id: Iaf0039c2be9bccb6cee11c24a3b44d209101fe47 Signed-off-by: José Bollo --- security/smack/smack_lsm.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c index b47fd5f..e6c0a57 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -960,18 +960,20 @@ static void smack_inode_post_setxattr(struct dentry *dentry, const char *name, return; } - skp = smk_import_entry(value, size); if (strcmp(name, XATTR_NAME_SMACK) == 0) { + skp = smk_import_entry(value, size); if (skp != NULL) isp->smk_inode = skp->smk_known; else isp->smk_inode = smack_known_invalid.smk_known; } else if (strcmp(name, XATTR_NAME_SMACKEXEC) == 0) { + skp = smk_import_entry(value, size); if (skp != NULL) isp->smk_task = skp; else isp->smk_task = &smack_known_invalid; } else if (strcmp(name, XATTR_NAME_SMACKMMAP) == 0) { + skp = smk_import_entry(value, size); if (skp != NULL) isp->smk_mmap = skp; else -- 2.1.4