Revision 7fb5409df092589b86cc9412d926879cb572b7f0 authored by Jan Kara on 10 February 2008, 06:08:38 UTC, committed by Theodore Ts'o on 10 February 2008, 06:08:38 UTC
We cannot start transaction in ext4_direct_IO() and just let it last during the whole write because dio_get_page() acquires mmap_sem which ranks above transaction start (e.g. because we have dependency chain mmap_sem->PageLock->journal_start, or because we update atime while holding mmap_sem) and thus deadlocks could happen. We solve the problem by starting a transaction separately for each ext4_get_block() call. We *could* have a problem that we allocate a block and before its data are written out the machine crashes and thus we expose stale data. But that does not happen because for hole-filling generic code falls back to buffered writes and for file extension, we add inode to orphan list and thus in case of crash, journal replay will truncate inode back to the original size. Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Mingming Cao <cmm@us.ibm.com> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
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Kconfig
#
# Security configuration
#
menu "Security options"
config KEYS
bool "Enable access key retention support"
help
This option provides support for retaining authentication tokens and
access keys in the kernel.
It also includes provision of methods by which such keys might be
associated with a process so that network filesystems, encryption
support and the like can find them.
Furthermore, a special type of key is available that acts as keyring:
a searchable sequence of keys. Each process is equipped with access
to five standard keyrings: UID-specific, GID-specific, session,
process and thread.
If you are unsure as to whether this is required, answer N.
config KEYS_DEBUG_PROC_KEYS
bool "Enable the /proc/keys file by which keys may be viewed"
depends on KEYS
help
This option turns on support for the /proc/keys file - through which
can be listed all the keys on the system that are viewable by the
reading process.
The only keys included in the list are those that grant View
permission to the reading process whether or not it possesses them.
Note that LSM security checks are still performed, and may further
filter out keys that the current process is not authorised to view.
Only key attributes are listed here; key payloads are not included in
the resulting table.
If you are unsure as to whether this is required, answer N.
config SECURITY
bool "Enable different security models"
depends on SYSFS
help
This allows you to choose different security modules to be
configured into your kernel.
If this option is not selected, the default Linux security
model will be used.
If you are unsure how to answer this question, answer N.
config SECURITY_NETWORK
bool "Socket and Networking Security Hooks"
depends on SECURITY
help
This enables the socket and networking security hooks.
If enabled, a security module can use these hooks to
implement socket and networking access controls.
If you are unsure how to answer this question, answer N.
config SECURITY_NETWORK_XFRM
bool "XFRM (IPSec) Networking Security Hooks"
depends on XFRM && SECURITY_NETWORK
help
This enables the XFRM (IPSec) networking security hooks.
If enabled, a security module can use these hooks to
implement per-packet access controls based on labels
derived from IPSec policy. Non-IPSec communications are
designated as unlabelled, and only sockets authorized
to communicate unlabelled data can send without using
IPSec.
If you are unsure how to answer this question, answer N.
config SECURITY_CAPABILITIES
bool "Default Linux Capabilities"
depends on SECURITY
default y
help
This enables the "default" Linux capabilities functionality.
If you are unsure how to answer this question, answer Y.
config SECURITY_FILE_CAPABILITIES
bool "File POSIX Capabilities (EXPERIMENTAL)"
depends on (SECURITY=n || SECURITY_CAPABILITIES!=n) && EXPERIMENTAL
default n
help
This enables filesystem capabilities, allowing you to give
binaries a subset of root's powers without using setuid 0.
If in doubt, answer N.
config SECURITY_ROOTPLUG
bool "Root Plug Support"
depends on USB=y && SECURITY
help
This is a sample LSM module that should only be used as such.
It prevents any programs running with egid == 0 if a specific
USB device is not present in the system.
See <http://www.linuxjournal.com/article.php?sid=6279> for
more information about this module.
If you are unsure how to answer this question, answer N.
config SECURITY_DEFAULT_MMAP_MIN_ADDR
int "Low address space to protect from user allocation"
depends on SECURITY
default 0
help
This is the portion of low virtual memory which should be protected
from userspace allocation. Keeping a user from writing to low pages
can help reduce the impact of kernel NULL pointer bugs.
For most users with lots of address space a value of 65536 is
reasonable and should cause no problems. Programs which use vm86
functionality would either need additional permissions from either
the LSM or the capabilities module or have this protection disabled.
This value can be changed after boot using the
/proc/sys/vm/mmap_min_addr tunable.
source security/selinux/Kconfig
source security/smack/Kconfig
endmenu
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