On Fri, 2014-10-24 at 10:07 +0300, Dmitry Kasatkin wrote: > ima_inode_setxattr() can be called with no value. Function does not > check the length so that following command can be used to produce > kernel oops: setfattr -n security.ima FOO. This patch fixes it. > > Changes in v2: > * testing validity of xattr type > * allow setting hash only in fix or log mode (Mimi)
I only mentioned "fix" mode, not "log" mode (explanation below). > > [ 261.562522] BUG: unable to handle kernel NULL pointer dereference at > (null) > [ 261.564109] IP: [<ffffffff812af272>] ima_inode_setxattr+0x3e/0x5a > [ 261.564109] PGD 3112f067 PUD 42965067 PMD 0 > [ 261.564109] Oops: 0000 [#1] SMP > [ 261.564109] Modules linked in: bridge stp llc evdev serio_raw i2c_piix4 > button fuse > [ 261.564109] CPU: 0 PID: 3299 Comm: setxattr Not tainted 3.16.0-kds+ #2924 > [ 261.564109] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 > [ 261.564109] task: ffff8800428c2430 ti: ffff880042be0000 task.ti: > ffff880042be0000 > [ 261.564109] RIP: 0010:[<ffffffff812af272>] [<ffffffff812af272>] > ima_inode_setxattr+0x3e/0x5a > [ 261.564109] RSP: 0018:ffff880042be3d50 EFLAGS: 00010246 > [ 261.564109] RAX: 0000000000000001 RBX: 0000000000000000 RCX: > 0000000000000015 > [ 261.564109] RDX: 0000001500000000 RSI: 0000000000000000 RDI: > ffff8800375cc600 > [ 261.564109] RBP: ffff880042be3d68 R08: 0000000000000000 R09: > 00000000004d6256 > [ 261.564109] R10: 0000000000000000 R11: 0000000000000000 R12: > ffff88002149ba00 > [ 261.564109] R13: 0000000000000000 R14: 0000000000000000 R15: > 0000000000000000 > [ 261.564109] FS: 00007f6c1e219740(0000) GS:ffff88005da00000(0000) > knlGS:0000000000000000 > [ 261.564109] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 261.564109] CR2: 0000000000000000 CR3: 000000003b35a000 CR4: > 00000000000006f0 > [ 261.564109] Stack: > [ 261.564109] ffff88002149ba00 ffff880042be3df8 0000000000000000 > ffff880042be3d98 > [ 261.564109] ffffffff812a101b ffff88002149ba00 ffff880042be3df8 > 0000000000000000 > [ 261.564109] 0000000000000000 ffff880042be3de0 ffffffff8116d08a > ffff880042be3dc8 > [ 261.564109] Call Trace: > [ 261.564109] [<ffffffff812a101b>] security_inode_setxattr+0x48/0x6a > [ 261.564109] [<ffffffff8116d08a>] vfs_setxattr+0x6b/0x9f > [ 261.564109] [<ffffffff8116d1e0>] setxattr+0x122/0x16c > [ 261.564109] [<ffffffff811687e8>] ? mnt_want_write+0x21/0x45 > [ 261.564109] [<ffffffff8114d011>] ? __sb_start_write+0x10f/0x143 > [ 261.564109] [<ffffffff811687e8>] ? mnt_want_write+0x21/0x45 > [ 261.564109] [<ffffffff811687c0>] ? __mnt_want_write+0x48/0x4f > [ 261.564109] [<ffffffff8116d3e6>] SyS_setxattr+0x6e/0xb0 > [ 261.564109] [<ffffffff81529da9>] system_call_fastpath+0x16/0x1b > [ 261.564109] Code: 48 89 f7 48 c7 c6 58 36 81 81 53 31 db e8 73 27 04 00 85 > c0 75 28 bf 15 00 00 00 e8 8a a5 d9 ff 84 c0 75 05 83 cb ff eb 15 31 f6 <41> > 80 7d 00 03 49 8b 7c 24 68 40 0f 94 c6 e8 e1 f9 ff ff 89 d8 > [ 261.564109] RIP [<ffffffff812af272>] ima_inode_setxattr+0x3e/0x5a > [ 261.564109] RSP <ffff880042be3d50> > [ 261.564109] CR2: 0000000000000000 > [ 261.599998] ---[ end trace 39a89a3fc267e652 ]--- > > Reported-by: Jan Kara <[email protected]> > Signed-off-by: Dmitry Kasatkin <[email protected]> > --- > security/integrity/ima/ima_appraise.c | 13 +++++++++++-- > 1 file changed, 11 insertions(+), 2 deletions(-) > > diff --git a/security/integrity/ima/ima_appraise.c > b/security/integrity/ima/ima_appraise.c > index 9226854..e302cbf 100644 > --- a/security/integrity/ima/ima_appraise.c > +++ b/security/integrity/ima/ima_appraise.c > @@ -378,8 +378,17 @@ int ima_inode_setxattr(struct dentry *dentry, const char > *xattr_name, > result = ima_protect_xattr(dentry, xattr_name, xattr_value, > xattr_value_len); > if (result == 1) { > - ima_reset_appraise_flags(dentry->d_inode, > - (xvalue->type == EVM_IMA_XATTR_DIGSIG) ? 1 : 0); > + bool digsig; > + > + if (!xattr_value_len || > + (xvalue->type != IMA_XATTR_DIGEST && > + xvalue->type != IMA_XATTR_DIGEST_NG && > + xvalue->type != EVM_IMA_XATTR_DIGSIG)) "xvalue->type" is an enumerated type. Testing each possible value seems kind of a brittle method for vetting the value. I suggest testing the existing last value or, better yet, define a last value, so if someone adds or changes the order, nothing breaks. > + return -EINVAL; > + digsig = (xvalue->type == EVM_IMA_XATTR_DIGSIG); > + if (!digsig && (ima_appraise & IMA_APPRAISE_ENFORCE)) > + return -EPERM; According to the new ima_appraise "log" mode, commit "2faa6ef ima: provide 'ima_appraise=log' kernel option", "log" mode permits normal execution without "fixing" anything. Normal execution, here, prevents writing the extended attribute. Mimi > + ima_reset_appraise_flags(dentry->d_inode, digsig); > result = 0; > } > return result; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
