kernel/lib/string.c, branch linux-5.2.y

lib/string: Add strscpy_pad() function

2019-04-08T22:44:21Z

We have a function to copy strings safely and we have a function to copy strings and zero the tail of the destination (if source string is shorter than destination buffer) but we do not have a function to do both at once. This means developers must write this themselves if they desire this functionality. This is a chore, and also leaves us open to off by one errors unnecessarily. Add a function that calls strscpy() then memset()s the tail to zero if the source string is shorter than the destination buffer. Acked-by: Kees Cook Signed-off-by: Tobin C. Harding Signed-off-by: Shuah Khan

lib/string.c: implement a basic bcmp

2019-04-06T02:02:30Z

A recent optimization in Clang (r355672) lowers comparisons of the return value of memcmp against zero to comparisons of the return value of bcmp against zero. This helps some platforms that implement bcmp more efficiently than memcmp. glibc simply aliases bcmp to memcmp, but an optimized implementation is in the works. This results in linkage failures for all targets with Clang due to the undefined symbol. For now, just implement bcmp as a tailcail to memcmp to unbreak the build. This routine can be further optimized in the future. Other ideas discussed: * A weak alias was discussed, but breaks for architectures that define their own implementations of memcmp since aliases to declarations are not permitted (only definitions). Arch-specific memcmp implementations typically declare memcmp in C headers, but implement them in assembly. * -ffreestanding also is used sporadically throughout the kernel. * -fno-builtin-bcmp doesn't work when doing LTO. Link: https://bugs.llvm.org/show_bug.cgi?id=41035 Link: https://code.woboq.org/userspace/glibc/string/memcmp.c.html#bcmp Link: https://github.com/llvm/llvm-project/commit/8e16d73346f8091461319a7dfc4ddd18eedcff13 Link: https://github.com/ClangBuiltLinux/linux/issues/416 Link: http://lkml.kernel.org/r/20190313211335.165605-1-ndesaulniers@google.com Signed-off-by: Nick Desaulniers Reported-by: Nathan Chancellor Reported-by: Adhemerval Zanella Suggested-by: Arnd Bergmann Suggested-by: James Y Knight Suggested-by: Masahiro Yamada Suggested-by: Nathan Chancellor Suggested-by: Rasmus Villemoes Acked-by: Steven Rostedt (VMware) Reviewed-by: Nathan Chancellor Tested-by: Nathan Chancellor Reviewed-by: Masahiro Yamada Reviewed-by: Andy Shevchenko Cc: David Laight Cc: Rasmus Villemoes Cc: Namhyung Kim Cc: Greg Kroah-Hartman Cc: Alexander Shishkin Cc: Dan Williams Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

lib: Fix ia64 bootloader linkage

2018-10-16T11:45:44Z

kbuild robot reports that since commit ce76d938dd98 ("lib: Add memcat_p(): paste 2 pointer arrays together") the ia64/hp/sim/boot fails to link: > LD arch/ia64/hp/sim/boot/bootloader > lib/string.o: In function `__memcat_p': > string.c:(.text+0x1f22): undefined reference to `__kmalloc' > string.c:(.text+0x1ff2): undefined reference to `__kmalloc' > make[1]: *** [arch/ia64/hp/sim/boot/Makefile:37: arch/ia64/hp/sim/boot/bootloader] Error 1 The reason is, the above commit, via __memcat_p(), adds a call to __kmalloc to string.o, which happens to be used in the bootloader, but there's no kmalloc or slab or anything. Since the linker would only pull in objects that contain referenced symbols, moving __memcat_p() to a different compilation unit solves the problem. Fixes: ce76d938dd98 ("lib: Add memcat_p(): paste 2 pointer arrays together") Signed-off-by: Alexander Shishkin Reported-by: kbuild test robot Cc: Fenghua Yu Cc: Tony Luck Cc: Joe Perches Signed-off-by: Greg Kroah-Hartman

lib: Add memcat_p(): paste 2 pointer arrays together

2018-10-11T10:12:55Z

This adds a helper to paste 2 pointer arrays together, useful for merging various types of attribute arrays. There are a few places in the kernel tree where this is open coded, and I just added one more in the STM class. The naming is inspired by memset_p() and memcat(), and partial credit for it goes to Andy Shevchenko. This patch adds the function wrapped in a type-enforcing macro and a test module. Signed-off-by: Alexander Shishkin Reviewed-by: Andy Shevchenko Tested-by: Mathieu Poirier Signed-off-by: Greg Kroah-Hartman

lib/strscpy: Shut up KASAN false-positives in strscpy()

2018-02-01T20:20:21Z

strscpy() performs the word-at-a-time optimistic reads. So it may may access the memory past the end of the object, which is perfectly fine since strscpy() doesn't use that (past-the-end) data and makes sure the optimistic read won't cross a page boundary. Use new read_word_at_a_time() to shut up the KASAN. Note that this potentially could hide some bugs. In example bellow, stscpy() will copy more than we should (1-3 extra uninitialized bytes): char dst[8]; char *src; src = kmalloc(5, GFP_KERNEL); memset(src, 0xff, 5); strscpy(dst, src, 8); Signed-off-by: Andrey Ryabinin Signed-off-by: Linus Torvalds

lib: add module support to string tests

2017-11-18T00:10:01Z

Extract the string test code into its own source file, to allow compiling it either to a loadable module, or built into the kernel. Fixes: 03270c13c5ffaa6a ("lib/string.c: add testcases for memset16/32/64") Link: http://lkml.kernel.org/r/1505397744-3387-1-git-send-email-geert@linux-m68k.org Signed-off-by: Geert Uytterhoeven Cc: Matthew Wilcox Cc: Shuah Khan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

License cleanup: add SPDX GPL-2.0 license identifier to files with no license

2017-11-02T10:10:55Z

Many source files in the tree are missing licensing information, which makes it harder for compliance tools to determine the correct license. By default all files without license information are under the default license of the kernel, which is GPL version 2. Update the files which contain no license information with the 'GPL-2.0' SPDX license identifier. The SPDX identifier is a legally binding shorthand, which can be used instead of the full boiler plate text. This patch is based on work done by Thomas Gleixner and Kate Stewart and Philippe Ombredanne. How this work was done: Patches were generated and checked against linux-4.14-rc6 for a subset of the use cases: - file had no licensing information it it. - file was a */uapi/* one with no licensing information in it, - file was a */uapi/* one with existing licensing information, Further patches will be generated in subsequent months to fix up cases where non-standard license headers were used, and references to license had to be inferred by heuristics based on keywords. The analysis to determine which SPDX License Identifier to be applied to a file was done in a spreadsheet of side by side results from of the output of two independent scanners (ScanCode & Windriver) producing SPDX tag:value files created by Philippe Ombredanne. Philippe prepared the base worksheet, and did an initial spot review of a few 1000 files. The 4.13 kernel was the starting point of the analysis with 60,537 files assessed. Kate Stewart did a file by file comparison of the scanner results in the spreadsheet to determine which SPDX license identifier(s) to be applied to the file. She confirmed any determination that was not immediately clear with lawyers working with the Linux Foundation. Criteria used to select files for SPDX license identifier tagging was: - Files considered eligible had to be source code files. - Make and config files were included as candidates if they contained >5 lines of source - File already had some variant of a license header in it (even if <5 lines). All documentation files were explicitly excluded. The following heuristics were used to determine which SPDX license identifiers to apply. - when both scanners couldn't find any license traces, file was considered to have no license information in it, and the top level COPYING file license applied. For non */uapi/* files that summary was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 11139 and resulted in the first patch in this series. If that file was a */uapi/* path one, it was "GPL-2.0 WITH Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 WITH Linux-syscall-note 930 and resulted in the second patch in this series. - if a file had some form of licensing information in it, and was one of the */uapi/* ones, it was denoted with the Linux-syscall-note if any GPL family license was found in the file or had no licensing in it (per prior point). Results summary: SPDX license identifier # files ---------------------------------------------------|------ GPL-2.0 WITH Linux-syscall-note 270 GPL-2.0+ WITH Linux-syscall-note 169 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17 LGPL-2.1+ WITH Linux-syscall-note 15 GPL-1.0+ WITH Linux-syscall-note 14 ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5 LGPL-2.0+ WITH Linux-syscall-note 4 LGPL-2.1 WITH Linux-syscall-note 3 ((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3 ((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1 and that resulted in the third patch in this series. - when the two scanners agreed on the detected license(s), that became the concluded license(s). - when there was disagreement between the two scanners (one detected a license but the other didn't, or they both detected different licenses) a manual inspection of the file occurred. - In most cases a manual inspection of the information in the file resulted in a clear resolution of the license that should apply (and which scanner probably needed to revisit its heuristics). - When it was not immediately clear, the license identifier was confirmed with lawyers working with the Linux Foundation. - If there was any question as to the appropriate license identifier, the file was flagged for further research and to be revisited later in time. In total, over 70 hours of logged manual review was done on the spreadsheet to determine the SPDX license identifiers to apply to the source files by Kate, Philippe, Thomas and, in some cases, confirmation by lawyers working with the Linux Foundation. Kate also obtained a third independent scan of the 4.13 code base from FOSSology, and compared selected files where the other two scanners disagreed against that SPDX file, to see if there was new insights. The Windriver scanner is based on an older version of FOSSology in part, so they are related. Thomas did random spot checks in about 500 files from the spreadsheets for the uapi headers and agreed with SPDX license identifier in the files he inspected. For the non-uapi files Thomas did random spot checks in about 15000 files. In initial set of patches against 4.14-rc6, 3 files were found to have copy/paste license identifier errors, and have been fixed to reflect the correct identifier. Additionally Philippe spent 10 hours this week doing a detailed manual inspection and review of the 12,461 patched files from the initial patch version early this week with: - a full scancode scan run, collecting the matched texts, detected license ids and scores - reviewing anything where there was a license detected (about 500+ files) to ensure that the applied SPDX license was correct - reviewing anything where there was no detection but the patch license was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied SPDX license was correct This produced a worksheet with 20 files needing minor correction. This worksheet was then exported into 3 different .csv files for the different types of files to be modified. These .csv files were then reviewed by Greg. Thomas wrote a script to parse the csv files and add the proper SPDX tag to the file, in the format that the file expected. This script was further refined by Greg based on the output to detect more types of files automatically and to distinguish between header and source .c files (which need different comment types.) Finally Greg ran the script using the .csv files to generate the patches. Reviewed-by: Kate Stewart Reviewed-by: Philippe Ombredanne Reviewed-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman

lib/string.c: check for kmalloc() failure

2017-09-09T01:26:49Z

This is mostly to keep the number of static checker warnings down so we can spot new bugs instead of them being drowned in noise. This function doesn't return normal kernel error codes but instead the return value is used to display exactly which memory failed. I chose -1 as hopefully that's a helpful thing to print. Link: http://lkml.kernel.org/r/20170817115420.uikisjvfmtrqkzjn@mwanda Signed-off-by: Dan Carpenter Cc: Matthew Wilcox Cc: Stephen Rothwell Cc: Kees Cook Cc: Bjorn Helgaas Cc: Mauro Carvalho Chehab Cc: Heikki Krogerus Cc: Daniel Micay Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

lib/string.c: add testcases for memset16/32/64

2017-09-09T01:26:48Z

[akpm@linux-foundation.org: minor tweaks] Link: http://lkml.kernel.org/r/20170720184539.31609-3-willy@infradead.org Signed-off-by: Matthew Wilcox Cc: "H. Peter Anvin" Cc: "James E.J. Bottomley" Cc: "Martin K. Petersen" Cc: David Miller Cc: Ingo Molnar Cc: Ivan Kokshaysky Cc: Matt Turner Cc: Michael Ellerman Cc: Minchan Kim Cc: Ralf Baechle Cc: Richard Henderson Cc: Russell King Cc: Sam Ravnborg Cc: Sergey Senozhatsky Cc: Thomas Gleixner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

lib/string.c: add multibyte memset functions

2017-09-09T01:26:48Z

Patch series "Multibyte memset variations", v4. A relatively common idiom we're missing is a function to fill an area of memory with a pattern which is larger than a single byte. I first noticed this with a zram patch which wanted to fill a page with an 'unsigned long' value. There turn out to be quite a few places in the kernel which can benefit from using an optimised function rather than a loop; sometimes text size, sometimes speed, and sometimes both. The optimised PowerPC version (not included here) improves performance by about 30% on POWER8 on just the raw memset_l(). Most of the extra lines of code come from the three testcases I added. This patch (of 8): memset16(), memset32() and memset64() are like memset(), but allow the caller to fill the destination with a value larger than a single byte. memset_l() and memset_p() allow the caller to use unsigned long and pointer values respectively. Link: http://lkml.kernel.org/r/20170720184539.31609-2-willy@infradead.org Signed-off-by: Matthew Wilcox Cc: "H. Peter Anvin" Cc: "James E.J. Bottomley" Cc: "Martin K. Petersen" Cc: David Miller Cc: Ingo Molnar Cc: Ivan Kokshaysky Cc: Matt Turner Cc: Michael Ellerman Cc: Minchan Kim Cc: Ralf Baechle Cc: Richard Henderson Cc: Russell King Cc: Sam Ravnborg Cc: Sergey Senozhatsky Cc: Thomas Gleixner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds