Sorry, this was the wrong version of the patch. Please ignore this patch and use what is in the reply to this patch: [PATCH v3 1/1] evm: check xattr value length and type in evm_inode_setxattr()
- Dmitry On 28/10/14 13:31, Dmitry Kasatkin wrote: > evm_inode_setxattr() can be called with no value. The function does not > check the length so that following command can be used to produce the > 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 <[email protected]> > Signed-off-by: Dmitry Kasatkin <[email protected]> > Cc: [email protected] > --- > 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); > } -- 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/
