[ 08/46] evm: checking if removexattr is not a NULL

Greg Kroah-Hartman
2013-01-24T21:14:48Z

From: Dmitry Kasatkin <dmitry.kasatkin@intel.com>

commit a67adb997419fb53540d4a4f79c6471c60bc69b6 upstream.

The following lines of code produce a kernel oops.

fd = socket(PF_FILE, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
fchmod(fd, 0666);

[ 139.922364] BUG: unable to handle kernel NULL pointer dereference at (null)
[ 139.924982] IP: [< (null)>] (null)
[ 139.924982] *pde = 00000000
[ 139.924982] Oops: 0000 [#5] SMP
[ 139.924982] Modules linked in: fuse dm_crypt dm_mod i2c_piix4 serio_raw evdev binfmt_misc button
[ 139.924982] Pid: 3070, comm: acpid Tainted: G D 3.8.0-rc2-kds+ #465 Bochs Bochs
[ 139.924982] EIP: 0060:[<00000000>] EFLAGS: 00010246 CPU: 0
[ 139.924982] EIP is at 0x0
[ 139.924982] EAX: cf5ef000 EBX: cf5ef000 ECX: c143d600 EDX: c15225f2
[ 139.924982] ESI: cf4d2a1c EDI: cf4d2a1c EBP: cc02df10 ESP: cc02dee4
[ 139.924982] DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
[ 139.924982] CR0: 80050033 CR2: 00000000 CR3: 0c059000 CR4: 000006d0
[ 139.924982] DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000
[ 139.924982] DR6: ffff0ff0 DR7: 00000400
[ 139.924982] Process acpid (pid: 3070, ti=cc02c000 task=d7705340 task.ti=cc02c000)
[ 139.924982] Stack:
[ 139.924982] c1203c88 00000000 cc02def4 cf4d2a1c ae21eefa 471b60d5 1083c1ba c26a5940
[ 139.924982] e891fb5e 00000041 00000004 cc02df1c c1203964 00000000 cc02df4c c10e20c3
[ 139.924982] 00000002 00000000 00000000 22222222 c1ff2222 cf5ef000 00000000 d76efb08
[ 139.924982] Call Trace:
[ 139.924982] [<c1203c88>] ? evm_update_evmxattr+0x5b/0x62
[ 139.924982] [<c1203964>] evm_inode_post_setattr+0x22/0x26
[ 139.924982] [<c10e20c3>] notify_change+0x25f/0x281
[ 139.924982] [<c10cbf56>] chmod_common+0x59/0x76
[ 139.924982] [<c10e27a1>] ? put_unused_fd+0x33/0x33
[ 139.924982] [<c10cca09>] sys_fchmod+0x39/0x5c
[ 139.924982] [<c13f4f30>] syscall_call+0x7/0xb
[ 139.924982] Code: Bad EIP value.

This happens because sockets do not define the removexattr operation.
Before removing the xattr, verify the removexattr function pointer is
not NULL.

Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@intel.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
security/integrity/evm/evm_crypto.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/security/integrity/evm/evm_crypto.c
+++ b/security/integrity/evm/evm_crypto.c
@@ -205,9 +205,9 @@ int evm_update_evmxattr(struct dentry *d
rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_EVM,
&xattr_data,
sizeof(xattr_data), 0);
- }
- else if (rc == -ENODATA)
+ } else if (rc == -ENODATA && inode->i_op->removexattr) {
rc = inode->i_op->removexattr(dentry, XATTR_NAME_EVM);
+ }
return rc;
}