user/sven/linux.git/kernel/kcov.c, branch v4.19.207

kernel/kcov.c: mark write_comp_data() as notrace

2019-02-12T18:47:20Z

[ Upstream commit 634724431607f6f46c495dfef801a1c8b44a96d9 ] Since __sanitizer_cov_trace_const_cmp4 is marked as notrace, the function called from __sanitizer_cov_trace_const_cmp4 shouldn't be traceable either. ftrace_graph_caller() gets called every time func write_comp_data() gets called if it isn't marked 'notrace'. This is the backtrace from gdb: #0 ftrace_graph_caller () at ../arch/arm64/kernel/entry-ftrace.S:179 #1 0xffffff8010201920 in ftrace_caller () at ../arch/arm64/kernel/entry-ftrace.S:151 #2 0xffffff8010439714 in write_comp_data (type=5, arg1=0, arg2=0, ip=18446743524224276596) at ../kernel/kcov.c:116 #3 0xffffff8010439894 in __sanitizer_cov_trace_const_cmp4 (arg1=, arg2=) at ../kernel/kcov.c:188 #4 0xffffff8010201874 in prepare_ftrace_return (self_addr=18446743524226602768, parent=0xffffff801014b918, frame_pointer=18446743524223531344) at ./include/generated/atomic-instrumented.h:27 #5 0xffffff801020194c in ftrace_graph_caller () at ../arch/arm64/kernel/entry-ftrace.S:182 Rework so that write_comp_data() that are called from __sanitizer_cov_trace_*_cmp*() are marked as 'notrace'. Commit 903e8ff86753 ("kernel/kcov.c: mark funcs in __sanitizer_cov_trace_pc() as notrace") missed to mark write_comp_data() as 'notrace'. When that patch was created gcc-7 was used. In lib/Kconfig.debug config KCOV_ENABLE_COMPARISONS depends on $(cc-option,-fsanitize-coverage=trace-cmp) That code path isn't hit with gcc-7. However, it were that with gcc-8. Link: http://lkml.kernel.org/r/20181206143011.23719-1-anders.roxell@linaro.org Signed-off-by: Anders Roxell Signed-off-by: Arnd Bergmann Co-developed-by: Arnd Bergmann Acked-by: Steven Rostedt (VMware) Cc: Will Deacon Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin

kernel/kcov.c: mark funcs in __sanitizer_cov_trace_pc() as notrace

2018-12-17T08:24:41Z

[ Upstream commit 903e8ff86753e6f327bb92166a0665e4ecb8e2e7 ] Since __sanitizer_cov_trace_pc() is marked as notrace, function calls in __sanitizer_cov_trace_pc() shouldn't be traced either. ftrace_graph_caller() gets called for each function that isn't marked 'notrace', like canonicalize_ip(). This is the call trace from a run: [ 139.644550] ftrace_graph_caller+0x1c/0x24 [ 139.648352] canonicalize_ip+0x18/0x28 [ 139.652313] __sanitizer_cov_trace_pc+0x14/0x58 [ 139.656184] sched_clock+0x34/0x1e8 [ 139.659759] trace_clock_local+0x40/0x88 [ 139.663722] ftrace_push_return_trace+0x8c/0x1f0 [ 139.667767] prepare_ftrace_return+0xa8/0x100 [ 139.671709] ftrace_graph_caller+0x1c/0x24 Rework so that check_kcov_mode() and canonicalize_ip() that are called from __sanitizer_cov_trace_pc() are also marked as notrace. Link: http://lkml.kernel.org/r/20181128081239.18317-1-anders.roxell@linaro.org Signed-off-by: Arnd Bergmann Signen-off-by: Anders Roxell Co-developed-by: Arnd Bergmann Acked-by: Steven Rostedt (VMware) Cc: Dmitry Vyukov Cc: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin

sched/core / kcov: avoid kcov_area during task switch

2018-06-14T22:55:24Z

During a context switch, we first switch_mm() to the next task's mm, then switch_to() that new task. This means that vmalloc'd regions which had previously been faulted in can transiently disappear in the context of the prev task. Functions instrumented by KCOV may try to access a vmalloc'd kcov_area during this window, and as the fault handling code is instrumented, this results in a recursive fault. We must avoid accessing any kcov_area during this window. We can do so with a new flag in kcov_mode, set prior to switching the mm, and cleared once the new task is live. Since task_struct::kcov_mode isn't always a specific enum kcov_mode value, this is made an unsigned int. The manipulation is hidden behind kcov_{prepare,finish}_switch() helpers, which are empty for !CONFIG_KCOV kernels. The code uses macros because I can't use static inline functions without a circular include dependency between and , since the definition of task_struct uses things defined in Link: http://lkml.kernel.org/r/20180504135535.53744-4-mark.rutland@arm.com Signed-off-by: Mark Rutland Acked-by: Andrey Ryabinin Cc: Dmitry Vyukov Cc: Ingo Molnar Cc: Peter Zijlstra Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kcov: prefault the kcov_area

2018-06-14T22:55:24Z

On many architectures the vmalloc area is lazily faulted in upon first access. This is problematic for KCOV, as __sanitizer_cov_trace_pc accesses the (vmalloc'd) kcov_area, and fault handling code may be instrumented. If an access to kcov_area faults, this will result in mutual recursion through the fault handling code and __sanitizer_cov_trace_pc(), eventually leading to stack corruption and/or overflow. We can avoid this by faulting in the kcov_area before __sanitizer_cov_trace_pc() is permitted to access it. Once it has been faulted in, it will remain present in the process page tables, and will not fault again. [akpm@linux-foundation.org: code cleanup] [akpm@linux-foundation.org: add comment explaining kcov_fault_in_area()] [akpm@linux-foundation.org: fancier code comment from Mark] Link: http://lkml.kernel.org/r/20180504135535.53744-3-mark.rutland@arm.com Signed-off-by: Mark Rutland Acked-by: Andrey Ryabinin Cc: Dmitry Vyukov Cc: Ingo Molnar Cc: Peter Zijlstra Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kcov: ensure irq code sees a valid area

2018-06-14T22:55:24Z

Patch series "kcov: fix unexpected faults". These patches fix a few issues where KCOV code could trigger recursive faults, discovered while debugging a patch enabling KCOV for arch/arm: * On CONFIG_PREEMPT kernels, there's a small race window where __sanitizer_cov_trace_pc() can see a bogus kcov_area. * Lazy faulting of the vmalloc area can cause mutual recursion between fault handling code and __sanitizer_cov_trace_pc(). * During the context switch, switching the mm can cause the kcov_area to be transiently unmapped. These are prerequisites for enabling KCOV on arm, but the issues themsevles are generic -- we just happen to avoid them by chance rather than design on x86-64 and arm64. This patch (of 3): For kernels built with CONFIG_PREEMPT, some C code may execute before or after the interrupt handler, while the hardirq count is zero. In these cases, in_task() can return true. A task can be interrupted in the middle of a KCOV_DISABLE ioctl while it resets the task's kcov data via kcov_task_init(). Instrumented code executed during this period will call __sanitizer_cov_trace_pc(), and as in_task() returns true, will inspect t->kcov_mode before trying to write to t->kcov_area. In kcov_init_task() we update t->kcov_{mode,area,size} with plain stores, which may be re-ordered, torn, etc. Thus __sanitizer_cov_trace_pc() may see bogus values for any of these fields, and may attempt to write to memory which is not mapped. Let's avoid this by using WRITE_ONCE() to set t->kcov_mode, with a barrier() to ensure this is ordered before we clear t->kov_{area,size}. This ensures that any code execute while kcov_init_task() is preempted will either see valid values for t->kcov_{area,size}, or will see that t->kcov_mode is KCOV_MODE_DISABLED, and bail out without touching t->kcov_area. Link: http://lkml.kernel.org/r/20180504135535.53744-2-mark.rutland@arm.com Signed-off-by: Mark Rutland Acked-by: Andrey Ryabinin Cc: Dmitry Vyukov Cc: Ingo Molnar Cc: Peter Zijlstra Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kcov: detect double association with a single task

2018-02-07T02:32:46Z

Currently KCOV_ENABLE does not check if the current task is already associated with another kcov descriptor. As the result it is possible to associate a single task with more than one kcov descriptor, which later leads to a memory leak of the old descriptor. This relation is really meant to be one-to-one (task has only one back link). Extend validation to detect such misuse. Link: http://lkml.kernel.org/r/20180122082520.15716-1-dvyukov@google.com Fixes: 5c9a8750a640 ("kernel: add kcov code coverage") Signed-off-by: Dmitry Vyukov Reported-by: Shankara Pailoor Cc: Dmitry Vyukov Cc: syzbot Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kcov: fix comparison callback signature

2017-12-15T00:00:48Z

Fix a silly copy-paste bug. We truncated u32 args to u16. Link: http://lkml.kernel.org/r/20171207101134.107168-1-dvyukov@google.com Fixes: ded97d2c2b2c ("kcov: support comparison operands collection") Signed-off-by: Dmitry Vyukov Cc: syzkaller@googlegroups.com Cc: Alexander Potapenko Cc: Vegard Nossum Cc: Quentin Casasnovas Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kcov: support comparison operands collection

2017-11-18T00:10:04Z

Enables kcov to collect comparison operands from instrumented code. This is done by using Clang's -fsanitize=trace-cmp instrumentation (currently not available for GCC). The comparison operands help a lot in fuzz testing. E.g. they are used in Syzkaller to cover the interiors of conditional statements with way less attempts and thus make previously unreachable code reachable. To allow separate collection of coverage and comparison operands two different work modes are implemented. Mode selection is now done via a KCOV_ENABLE ioctl call with corresponding argument value. Link: http://lkml.kernel.org/r/20171011095459.70721-1-glider@google.com Signed-off-by: Victor Chibotaru Signed-off-by: Alexander Potapenko Cc: Dmitry Vyukov Cc: Andrey Konovalov Cc: Mark Rutland Cc: Alexander Popov Cc: Andrey Ryabinin Cc: Kees Cook Cc: Vegard Nossum Cc: Quentin Casasnovas Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kcov: remove pointless current != NULL check

2017-11-18T00:10:04Z

__sanitizer_cov_trace_pc() is a hot code, so it's worth to remove pointless '!current' check. Current is never NULL. Link: http://lkml.kernel.org/r/20170929162221.32500-1-aryabinin@virtuozzo.com Signed-off-by: Andrey Ryabinin Acked-by: Dmitry Vyukov Acked-by: Mark Rutland Cc: Andrey Konovalov 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