From dd05add7b2b6004c5fa3a1f276f56d8668f86b65 Mon Sep 17 00:00:00 2001 From: Paulo Alcantara Date: Sat, 26 Sep 2026 19:20:30 -0300 Subject: netfs: zero the tail of a short DIO/unbuffered read The buffered read collector zero-fills the tail of a short read that stops below the inode's i_size (netfs_clear_unread()), so a read that races an extending write still returns the expected number of bytes. The non-buffered collector path does no such thing: it just records how much was transferred. Add the same zero-fill for the non-buffered case, gated on NETFS_SREQ_CLEAR_TAIL: a subreq's source sets that flag when a short result from it is known to be safe to treat as a hole, as opposed to NETFS_SREQ_HIT_EOF, which means the read genuinely ran off the end of the file and should be reported short as-is. Only CLEAR_TAIL should zero-fill here; a real EOF must stay a real short read. No source currently sets CLEAR_TAIL on an unbuffered/DIO subrequest, so this is inert on its own -- a following change teaches cifs to set it in the one case that needs it. Fixes: e2d46f2ec332 ("netfs: Change the read result collector to only use one work item") Reviewed-by: David Howells Reviewed-by: Namjae Jeon Signed-off-by: Paulo Alcantara Cc: Christian Brauner Cc: Matthew Wilcox Cc: Ronnie Sahlberg Cc: Shyam Prasad N Cc: Tom Talpey Cc: Bharath SM Cc: stable@vger.kernel.org --- lib/Kconfig.kmsan | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 54 insertions(+) create mode 100644 lib/Kconfig.kmsan (limited to 'lib/Kconfig.kmsan') diff --git a/lib/Kconfig.kmsan b/lib/Kconfig.kmsan new file mode 100644 index 000000000..cae1ddcc1 --- /dev/null +++ b/lib/Kconfig.kmsan @@ -0,0 +1,54 @@ +# SPDX-License-Identifier: GPL-2.0-only +config HAVE_ARCH_KMSAN + bool + +config HAVE_KMSAN_COMPILER + def_bool $(cc-option,-fsanitize=kernel-memory) + +config KMSAN + bool "KMSAN: detector of uninitialized values use" + depends on HAVE_ARCH_KMSAN && HAVE_KMSAN_COMPILER + depends on DEBUG_KERNEL && !KASAN && !KCSAN + depends on !PREEMPT_RT + select STACKDEPOT + select STACKDEPOT_ALWAYS_INIT + help + KernelMemorySanitizer (KMSAN) is a dynamic detector of uses of + uninitialized values in the kernel. It is based on compiler + instrumentation provided by Clang and thus requires Clang to build. + + An important note is that KMSAN is not intended for production use, + because it drastically increases kernel memory footprint and slows + the whole system down. + + See for more details. + +if KMSAN + +config KMSAN_CHECK_PARAM_RETVAL + bool "Check for uninitialized values passed to and returned from functions" + default y + help + If the compiler supports -fsanitize-memory-param-retval, KMSAN will + eagerly check every function parameter passed by value and every + function return value. + + Disabling KMSAN_CHECK_PARAM_RETVAL will result in tracking shadow for + function parameters and return values across function borders. This + is a more relaxed mode, but it generates more instrumentation code and + may potentially report errors in corner cases when non-instrumented + functions call instrumented ones. + +config KMSAN_KUNIT_TEST + tristate "KMSAN integration test suite" if !KUNIT_ALL_TESTS + default KUNIT_ALL_TESTS + depends on TRACEPOINTS && KUNIT + help + Test suite for KMSAN, testing various error detection scenarios, + and checking that reports are correctly output to console. + + Say Y here if you want the test to be built into the kernel and run + during boot; say M if you want the test to build as a module; say N + if you are unsure. + +endif -- cgit v1.3.1