linux/Documentation/sysctl/kernel.txt, branch v3.0.62

coredump: add support for exe_file in core name

2011-05-27T00:12:36Z

Now, exe_file is not proc FS dependent, so we can use it to name core file. So we add %E pattern for core file name cration which extract path from mm_struct->exe_file. Then it converts slashes to exclamation marks and pastes the result to the core file name itself. This is useful for environments where binary names are longer than 16 character (the current->comm limitation). Also where there are binaries with same name but in a different path. Further in case the binery itself changes its current->comm after exec. So by doing (s/$/#/ -- # is treated as git comment): $ sysctl kernel.core_pattern='core.%p.%e.%E' $ ln /bin/cat cat45678901234567890 $ ./cat45678901234567890 ^Z $ rm cat45678901234567890 $ fg ^\Quit (core dumped) $ ls core* we now get: core.2434.cat456789012345.!root!cat45678901234567890 (deleted) Signed-off-by: Jiri Slaby Cc: Al Viro Cc: Alan Cox Reviewed-by: Andi Kleen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Documentation: default_message_level is a typo

2011-02-11T14:14:10Z

It's default_message_loglevel, not default_message_level. Signed-off-by: Paul Bolle Signed-off-by: Jiri Kosina

kptr_restrict for hiding kernel pointers from unprivileged users

2011-01-13T16:03:08Z

Add the %pK printk format specifier and the /proc/sys/kernel/kptr_restrict sysctl. The %pK format specifier is designed to hide exposed kernel pointers, specifically via /proc interfaces. Exposing these pointers provides an easy target for kernel write vulnerabilities, since they reveal the locations of writable structures containing easily triggerable function pointers. The behavior of %pK depends on the kptr_restrict sysctl. If kptr_restrict is set to 0, no deviation from the standard %p behavior occurs. If kptr_restrict is set to 1, the default, if the current user (intended to be a reader via seq_printf(), etc.) does not have CAP_SYSLOG (currently in the LSM tree), kernel pointers using %pK are printed as 0's. If kptr_restrict is set to 2, kernel pointers using %pK are printed as 0's regardless of privileges. Replacing with 0's was chosen over the default "(null)", which cannot be parsed by userland %p, which expects "(nil)". [akpm@linux-foundation.org: check for IRQ context when !kptr_restrict, save an indent level, s/WARN/WARN_ONCE/] [akpm@linux-foundation.org: coding-style fixup] [randy.dunlap@oracle.com: fix kernel/sysctl.c warning] Signed-off-by: Dan Rosenberg Signed-off-by: Randy Dunlap Cc: James Morris Cc: Eric Dumazet Cc: Thomas Graf Cc: Eugene Teo Cc: Kees Cook Cc: Ingo Molnar Cc: David S. Miller Cc: Peter Zijlstra Cc: Eric Paris Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

syslog: check cap_syslog when dmesg_restrict

2010-12-08T22:48:48Z

Eric Paris pointed out that it doesn't make sense to require both CAP_SYS_ADMIN and CAP_SYSLOG for certain syslog actions. So require CAP_SYSLOG, not CAP_SYS_ADMIN, when dmesg_restrict is set. (I'm also consolidating the now common error path) Signed-off-by: Serge E. Hallyn Acked-by: Eric Paris Acked-by: Kees Cook Signed-off-by: James Morris

Restrict unprivileged access to kernel syslog

2010-11-12T15:55:32Z

The kernel syslog contains debugging information that is often useful during exploitation of other vulnerabilities, such as kernel heap addresses. Rather than futilely attempt to sanitize hundreds (or thousands) of printk statements and simultaneously cripple useful debugging functionality, it is far simpler to create an option that prevents unprivileged users from reading the syslog. This patch, loosely based on grsecurity's GRKERNSEC_DMESG, creates the dmesg_restrict sysctl. When set to "0", the default, no restrictions are enforced. When set to "1", only users with CAP_SYS_ADMIN can read the kernel syslog via dmesg(8) or other mechanisms. [akpm@linux-foundation.org: explain the config option in kernel.txt] Signed-off-by: Dan Rosenberg Acked-by: Ingo Molnar Acked-by: Eugene Teo Acked-by: Kees Cook Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

doc: Add documentation for bootloader_{type,version}

2009-12-11T22:28:56Z

Add documentation for kernel/bootloader_type and kernel/bootloader_version to sysctl/kernel.txt. This should really have been done a long time ago. Signed-off-by: H. Peter Anvin Cc: Shen Feng

docs: fix core_pipe_limit info

2009-11-09T08:40:55Z

Fix typos in core_pipe_limit info. Signed-off-by: Randy Dunlap Cc: Neil Horman Signed-off-by: Jiri Kosina

exec: let do_coredump() limit the number of concurrent dumps to pipes

2009-09-24T14:21:00Z

Introduce core pipe limiting sysctl. Since we can dump cores to pipe, rather than directly to the filesystem, we create a condition in which a user can create a very high load on the system simply by running bad applications. If the pipe reader specified in core_pattern is poorly written, we can have lots of ourstandig resources and processes in the system. This sysctl introduces an ability to limit that resource consumption. core_pipe_limit defines how many in-flight dumps may be run in parallel, dumps beyond this value are skipped and a note is made in the kernel log. A special value of 0 in core_pipe_limit denotes unlimited core dumps may be handled (this is the default value). [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Neil Horman Reported-by: Earl Chew Cc: Oleg Nesterov Cc: Andi Kleen Cc: Alan Cox Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

printk: add printk_delay to make messages readable for some scenarios

2009-09-23T14:39:28Z

When syslog is not possible, at the same time there's no serial/net console available, it will be hard to read the printk messages. For example oops/panic/warning messages in shutdown phase. Add a printk delay feature, we can make each printk message delay some milliseconds. Setting the delay by proc/sysctl interface: /proc/sys/kernel/printk_delay The value range from 0 - 10000, default value is 0 [akpm@linux-foundation.org: fix a few things] Signed-off-by: Dave Young Acked-by: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

trivial: doc: document missing value 2 for randomize-va-space

2009-09-21T13:14:53Z

The documentation for /proc/sys/kernel/* does not mention the possible value 2 for randomize-va-space yet. While being there, doing some reformatting, fixing grammar problems and clarifying the correlations between randomize-va-space, kernel parameter "norandmaps" and the CONFIG_COMPAT_BRK option. Signed-off-by: Horst Schirmeier Signed-off-by: Jiri Kosina