SMACK: Fix handling value==NULL in post setxattr
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>
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@ -960,18 +960,20 @@ static void smack_inode_post_setxattr(struct dentry *dentry, const char *name,
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return;
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}
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skp = smk_import_entry(value, size);
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if (strcmp(name, XATTR_NAME_SMACK) == 0) {
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skp = smk_import_entry(value, size);
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if (skp != NULL)
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isp->smk_inode = skp->smk_known;
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else
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isp->smk_inode = smack_known_invalid.smk_known;
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} else if (strcmp(name, XATTR_NAME_SMACKEXEC) == 0) {
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skp = smk_import_entry(value, size);
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if (skp != NULL)
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isp->smk_task = skp;
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else
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isp->smk_task = &smack_known_invalid;
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} else if (strcmp(name, XATTR_NAME_SMACKMMAP) == 0) {
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skp = smk_import_entry(value, size);
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if (skp != NULL)
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isp->smk_mmap = skp;
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else
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