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Commit b7f5ab6fbbb9459a91c0acae15097a495f800206

Authored by Horst Schirmeier
Committed by Jiri Kosina
1 parent 627df23c61
Exists in master and in 7 other branches imx_3.0.35_4.1.0, imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga, smarc-l5.0.0_1.0.0-ga

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

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 <horst@schirmeier.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

Showing 1 changed file with 17 additions and 13 deletions Side-by-side Diff

Documentation/sysctl/kernel.txt
Diff comments   View file @ b7f5ab6
... ... @@ -319,25 +319,29 @@
319 319 space randomization that is used in the system, for architectures
320 320 that support this feature.
321 321  
322   -0 - Turn the process address space randomization off by default.
  322 +0 - Turn the process address space randomization off. This is the
  323 + default for architectures that do not support this feature anyways,
  324 + and kernels that are booted with the "norandmaps" parameter.
323 325  
324 326 1 - Make the addresses of mmap base, stack and VDSO page randomized.
325 327 This, among other things, implies that shared libraries will be
326   - loaded to random addresses. Also for PIE-linked binaries, the location
327   - of code start is randomized.
  328 + loaded to random addresses. Also for PIE-linked binaries, the
  329 + location of code start is randomized. This is the default if the
  330 + CONFIG_COMPAT_BRK option is enabled.
328 331  
329   - With heap randomization, the situation is a little bit more
330   - complicated.
331   - There a few legacy applications out there (such as some ancient
  332 +2 - Additionally enable heap randomization. This is the default if
  333 + CONFIG_COMPAT_BRK is disabled.
  334 +
  335 + There are a few legacy applications out there (such as some ancient
332 336 versions of libc.so.5 from 1996) that assume that brk area starts
333   - just after the end of the code+bss. These applications break when
334   - start of the brk area is randomized. There are however no known
  337 + just after the end of the code+bss. These applications break when
  338 + start of the brk area is randomized. There are however no known
335 339 non-legacy applications that would be broken this way, so for most
336   - systems it is safe to choose full randomization. However there is
337   - a CONFIG_COMPAT_BRK option for systems with ancient and/or broken
338   - binaries, that makes heap non-randomized, but keeps all other
339   - parts of process address space randomized if randomize_va_space
340   - sysctl is turned on.
  340 + systems it is safe to choose full randomization.
  341 +
  342 + Systems with ancient and/or broken binaries should be configured
  343 + with CONFIG_COMPAT_BRK enabled, which excludes the heap from process
  344 + address space randomization.
341 345  
342 346 ==============================================================
343 347