Messages in this thread | | | Date | Fri, 11 Apr 2014 14:46:37 -0700 | From | Casey Schaufler <> | Subject | Re: [PATCH 1/1] SMACK: Fix handling value==NULL in post setxattr |
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On 4/3/2014 4:48 AM, José Bollo wrote: > 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 <jose.bollo@open.eurogiciel.org>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Applied to git://git.gitorious.org/smack-next/kernel.git smack-for-3.16
> --- > 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 3f01cf5..28d482c 100644 > --- a/security/smack/smack_lsm.c > +++ b/security/smack/smack_lsm.c > @@ -893,18 +893,20 @@ 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
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