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c637693b20
Make each UBSAN option individually selectable and remove UBSAN_MISC which no longer has any purpose. Add help text for each Kconfig, and include a reference to the Clang sanitizer documentation. Disable unsigned overflow by default (not available with GCC and makes x86 unbootable with Clang). Disable unreachable when objtool is in use (redundant and confuses things: instrumentation appears at unreachable locations). Link: https://lkml.kernel.org/r/20201203004437.389959-7-keescook@chromium.org Signed-off-by: Kees Cook <keescook@chromium.org> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> Cc: Ard Biesheuvel <ardb@kernel.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: George Popescu <georgepope@android.com> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Marco Elver <elver@google.com> Cc: Masahiro Yamada <masahiroy@kernel.org> Cc: Michal Marek <michal.lkml@markovi.net> Cc: Nathan Chancellor <natechancellor@gmail.com> Cc: Nick Desaulniers <ndesaulniers@google.com> Cc: Peter Oberparleiter <oberpar@linux.ibm.com> Cc: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
90 lines
3.2 KiB
ReStructuredText
90 lines
3.2 KiB
ReStructuredText
The Undefined Behavior Sanitizer - UBSAN
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========================================
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UBSAN is a runtime undefined behaviour checker.
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UBSAN uses compile-time instrumentation to catch undefined behavior (UB).
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Compiler inserts code that perform certain kinds of checks before operations
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that may cause UB. If check fails (i.e. UB detected) __ubsan_handle_*
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function called to print error message.
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GCC has that feature since 4.9.x [1_] (see ``-fsanitize=undefined`` option and
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its suboptions). GCC 5.x has more checkers implemented [2_].
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Report example
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--------------
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::
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================================================================================
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UBSAN: Undefined behaviour in ../include/linux/bitops.h:110:33
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shift exponent 32 is to large for 32-bit type 'unsigned int'
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CPU: 0 PID: 0 Comm: swapper Not tainted 4.4.0-rc1+ #26
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0000000000000000 ffffffff82403cc8 ffffffff815e6cd6 0000000000000001
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ffffffff82403cf8 ffffffff82403ce0 ffffffff8163a5ed 0000000000000020
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ffffffff82403d78 ffffffff8163ac2b ffffffff815f0001 0000000000000002
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Call Trace:
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[<ffffffff815e6cd6>] dump_stack+0x45/0x5f
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[<ffffffff8163a5ed>] ubsan_epilogue+0xd/0x40
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[<ffffffff8163ac2b>] __ubsan_handle_shift_out_of_bounds+0xeb/0x130
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[<ffffffff815f0001>] ? radix_tree_gang_lookup_slot+0x51/0x150
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[<ffffffff8173c586>] _mix_pool_bytes+0x1e6/0x480
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[<ffffffff83105653>] ? dmi_walk_early+0x48/0x5c
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[<ffffffff8173c881>] add_device_randomness+0x61/0x130
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[<ffffffff83105b35>] ? dmi_save_one_device+0xaa/0xaa
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[<ffffffff83105653>] dmi_walk_early+0x48/0x5c
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[<ffffffff831066ae>] dmi_scan_machine+0x278/0x4b4
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[<ffffffff8111d58a>] ? vprintk_default+0x1a/0x20
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[<ffffffff830ad120>] ? early_idt_handler_array+0x120/0x120
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[<ffffffff830b2240>] setup_arch+0x405/0xc2c
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[<ffffffff830ad120>] ? early_idt_handler_array+0x120/0x120
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[<ffffffff830ae053>] start_kernel+0x83/0x49a
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[<ffffffff830ad120>] ? early_idt_handler_array+0x120/0x120
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[<ffffffff830ad386>] x86_64_start_reservations+0x2a/0x2c
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[<ffffffff830ad4f3>] x86_64_start_kernel+0x16b/0x17a
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================================================================================
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Usage
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-----
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To enable UBSAN configure kernel with::
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CONFIG_UBSAN=y
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and to check the entire kernel::
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CONFIG_UBSAN_SANITIZE_ALL=y
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To enable instrumentation for specific files or directories, add a line
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similar to the following to the respective kernel Makefile:
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- For a single file (e.g. main.o)::
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UBSAN_SANITIZE_main.o := y
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- For all files in one directory::
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UBSAN_SANITIZE := y
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To exclude files from being instrumented even if
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``CONFIG_UBSAN_SANITIZE_ALL=y``, use::
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UBSAN_SANITIZE_main.o := n
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and::
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UBSAN_SANITIZE := n
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Detection of unaligned accesses controlled through the separate option -
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CONFIG_UBSAN_ALIGNMENT. It's off by default on architectures that support
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unaligned accesses (CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS=y). One could
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still enable it in config, just note that it will produce a lot of UBSAN
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reports.
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References
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----------
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.. _1: https://gcc.gnu.org/onlinedocs/gcc-4.9.0/gcc/Debugging-Options.html
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.. _2: https://gcc.gnu.org/onlinedocs/gcc/Debugging-Options.html
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.. _3: https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html
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