linux-dev - Linux kernel development work

Age	Commit message (Collapse)	Author	Files	Lines
2016-05-20	x86/kasan: instrument user memory access API	Andrey Ryabinin	1	-0/+2
	Exchange between user and kernel memory is coded in assembly language. Which means that such accesses won't be spotted by KASAN as a compiler instruments only C code. Add explicit KASAN checks to user memory access API to ensure that userspace writes to (or reads from) a valid kernel memory. Note: Unlike others strncpy_from_user() is written mostly in C and KASAN sees memory accesses in it. However, it makes sense to add explicit check for all @count bytes that potentially could be written to the kernel. [aryabinin@virtuozzo.com: move kasan check under the condition] Link: http://lkml.kernel.org/r/1462869209-21096-1-git-send-email-aryabinin@virtuozzo.com Link: http://lkml.kernel.org/r/1462538722-1574-4-git-send-email-aryabinin@virtuozzo.com Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com> Cc: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-12-17	Use the new batched user accesses in generic user string handling	Linus Torvalds	1	-3/+8
	This converts the generic user string functions to use the batched user access functions. It makes a big difference on Skylake, which is the first x86 microarchitecture to implement SMAP. The STAC/CLAC instructions are not very fast, and doing them for each access inside the loop that copies strings from user space (which is what the pathname handling does for every pathname the kernel uses, for example) is very inefficient. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-02-12	lib/strncpy_from_user.c: replace module.h include	Rasmus Villemoes	1	-1/+2
	strncpy_from_user.c only needs EXPORT_SYMBOL, so just include compiler.h and export.h instead of the whole module.h machinery. Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-05-26	word-at-a-time: make the interfaces truly generic	Linus Torvalds	1	-40/+7
	This changes the interfaces in <asm/word-at-a-time.h> to be a bit more complicated, but a lot more generic. In particular, it allows us to really do the operations efficiently on both little-endian and big-endian machines, pretty much regardless of machine details. For example, if you can rely on a fast population count instruction on your architecture, this will allow you to make your optimized <asm/word-at-a-time.h> file with that. NOTE! The "generic" version in include/asm-generic/word-at-a-time.h is not truly generic, it actually only works on big-endian. Why? Because on little-endian the generic algorithms are wasteful, since you can inevitably do better. The x86 implementation is an example of that. (The only truly non-generic part of the asm-generic implementation is the "find_zero()" function, and you could make a little-endian version of it. And if the Kbuild infrastructure allowed us to pick a particular header file, that would be lovely) The <asm/word-at-a-time.h> functions are as follows: - WORD_AT_A_TIME_CONSTANTS: specific constants that the algorithm uses. - has_zero(): take a word, and determine if it has a zero byte in it. It gets the word, the pointer to the constant pool, and a pointer to an intermediate "data" field it can set. This is the "quick-and-dirty" zero tester: it's what is run inside the hot loops. - "prep_zero_mask()": take the word, the data that has_zero() produced, and the constant pool, and generate an exact mask of which byte had the first zero. This is run directly outside the loop, and allows the "has_zero()" function to answer the "is there a zero byte" question without necessarily getting exactly which byte is the first one to contain a zero. If you do multiple byte lookups concurrently (eg "hash_name()", which looks for both NUL and '/' bytes), after you've done the prep_zero_mask() phase, the result of those can be or'ed together to get the "either or" case. - The result from "prep_zero_mask()" can then be fed into "find_zero()" (to find the byte offset of the first byte that was zero) or into "zero_bytemask()" (to find the bytemask of the bytes preceding the zero byte). The existence of zero_bytemask() is optional, and is not necessary for the normal string routines. But dentry name hashing needs it, so if you enable DENTRY_WORD_AT_A_TIME you need to expose it. This changes the generic strncpy_from_user() function and the dentry hashing functions to use these modified word-at-a-time interfaces. This gets us back to the optimized state of the x86 strncpy that we lost in the previous commit when moving over to the generic version. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-05-24	lib: Sparc's strncpy_from_user is generic enough, move under lib/	David S. Miller	1	-0/+146
	To use this, an architecture simply needs to: 1) Provide a user_addr_max() implementation via asm/uaccess.h 2) Add "select GENERIC_STRNCPY_FROM_USER" to their arch Kcnfig 3) Remove the existing strncpy_from_user() implementation and symbol exports their architecture had. Signed-off-by: David S. Miller <davem@davemloft.net> Acked-by: David Howells <dhowells@redhat.com>