Discussion:
[PATCH v2 0/2] integrity fixes
Dmitry Kasatkin
2014-10-24 07:07:04 UTC
Permalink
Hi,

At first I did not notice Mimi's email with suggestion to allow
setting hash only in fix mode. Here is a next set with checking
validity of xattr type and allowing setting hash only in permissive
modes such as fix and log.

- Dmitry

Dmitry Kasatkin (2):
ima: check xattr value length in ima_inode_setxattr()
evm: check xattr value length in evm_inode_setxattr()

security/integrity/evm/evm_main.c | 11 ++++++++---
security/integrity/ima/ima_appraise.c | 13 +++++++++++--
2 files changed, 19 insertions(+), 5 deletions(-)
--
1.9.1

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Dmitry Kasatkin
2014-10-24 07:07:05 UTC
Permalink
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)

[ 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 <***@suse.cz>
Signed-off-by: Dmitry Kasatkin <***@samsung.com>
---
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))
+ return -EINVAL;
+ digsig = (xvalue->type == EVM_IMA_XATTR_DIGSIG);
+ if (!digsig && (ima_appraise & IMA_APPRAISE_ENFORCE))
+ return -EPERM;
+ ima_reset_appraise_flags(dentry->d_inode, digsig);
result = 0;
}
return result;
--
1.9.1

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Dmitry Kasatkin
2014-10-24 07:07:06 UTC
Permalink
evm_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.evm FOO. This patch fixes it.

Changes in v2:
* testing for validity of xattr type

[ 1106.396921] BUG: unable to handle kernel NULL pointer dereference at (null)
[ 1106.398192] IP: [<ffffffff812af7b8>] evm_inode_setxattr+0x2a/0x48
[ 1106.399244] PGD 29048067 PUD 290d7067 PMD 0
[ 1106.399953] Oops: 0000 [#1] SMP
[ 1106.400020] Modules linked in: bridge stp llc evdev serio_raw i2c_piix4 button fuse
[ 1106.400020] CPU: 0 PID: 3635 Comm: setxattr Not tainted 3.16.0-kds+ #2936
[ 1106.400020] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[ 1106.400020] task: ffff8800291a0000 ti: ffff88002917c000 task.ti: ffff88002917c000
[ 1106.400020] RIP: 0010:[<ffffffff812af7b8>] [<ffffffff812af7b8>] evm_inode_setxattr+0x2a/0x48
[ 1106.400020] RSP: 0018:ffff88002917fd50 EFLAGS: 00010246
[ 1106.400020] RAX: 0000000000000000 RBX: ffff88002917fdf8 RCX: 0000000000000000
[ 1106.400020] RDX: 0000000000000000 RSI: ffffffff818136d3 RDI: ffff88002917fdf8
[ 1106.400020] RBP: ffff88002917fd68 R08: 0000000000000000 R09: 00000000003ec1df
[ 1106.400020] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8800438a0a00
[ 1106.400020] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
[ 1106.400020] FS: 00007f7dfa7d7740(0000) GS:ffff88005da00000(0000) knlGS:0000000000000000
[ 1106.400020] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 1106.400020] CR2: 0000000000000000 CR3: 000000003763e000 CR4: 00000000000006f0
[ 1106.400020] Stack:
[ 1106.400020] ffff8800438a0a00 ffff88002917fdf8 0000000000000000 ffff88002917fd98
[ 1106.400020] ffffffff812a1030 ffff8800438a0a00 ffff88002917fdf8 0000000000000000
[ 1106.400020] 0000000000000000 ffff88002917fde0 ffffffff8116d08a ffff88002917fdc8
[ 1106.400020] Call Trace:
[ 1106.400020] [<ffffffff812a1030>] security_inode_setxattr+0x5d/0x6a
[ 1106.400020] [<ffffffff8116d08a>] vfs_setxattr+0x6b/0x9f
[ 1106.400020] [<ffffffff8116d1e0>] setxattr+0x122/0x16c
[ 1106.400020] [<ffffffff811687e8>] ? mnt_want_write+0x21/0x45
[ 1106.400020] [<ffffffff8114d011>] ? __sb_start_write+0x10f/0x143
[ 1106.400020] [<ffffffff811687e8>] ? mnt_want_write+0x21/0x45
[ 1106.400020] [<ffffffff811687c0>] ? __mnt_want_write+0x48/0x4f
[ 1106.400020] [<ffffffff8116d3e6>] SyS_setxattr+0x6e/0xb0
[ 1106.400020] [<ffffffff81529da9>] system_call_fastpath+0x16/0x1b
[ 1106.400020] Code: c3 0f 1f 44 00 00 55 48 89 e5 41 55 49 89 d5 41 54 49 89 fc 53 48 89 f3 48 c7 c6 d3 36 81 81 48 89 df e8 18 22 04 00 85 c0 75 07 <41> 80 7d 00 02 74 0d 48 89 de 4c 89 e7 e8 5a fe ff ff eb 03 83
[ 1106.400020] RIP [<ffffffff812af7b8>] evm_inode_setxattr+0x2a/0x48
[ 1106.400020] RSP <ffff88002917fd50>
[ 1106.400020] CR2: 0000000000000000
[ 1106.428061] ---[ end trace ae08331628ba3050 ]---

Reported-by: Jan Kara <***@suse.cz>
Signed-off-by: Dmitry Kasatkin <***@samsung.com>
---
security/integrity/evm/evm_main.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index b392fe6..1384e4b 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -324,9 +324,14 @@ int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name,
{
const struct evm_ima_xattr_data *xattr_data = xattr_value;

- if ((strcmp(xattr_name, XATTR_NAME_EVM) == 0)
- && (xattr_data->type == EVM_XATTR_HMAC))
- return -EPERM;
+ if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
+ if (!xattr_value_len)
+ return -EINVAL;
+ if (xattr_data->type == EVM_XATTR_HMAC)
+ return -EPERM;
+ if (xattr_data->type != EVM_IMA_XATTR_DIGSIG)
+ return -EINVAL;
+ }
return evm_protect_xattr(dentry, xattr_name, xattr_value,
xattr_value_len);
}
--
1.9.1
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