From: Jeff King <peff@peff•net>
To: git@vger•kernel.org
Cc: Patrick Steinhardt <ps@pks•im>, correctmost <cmlists@sent•com>,
Taylor Blau <me@ttaylorr•com>
Subject: [PATCH v2 3/9] Makefile: turn on NO_MMAP when building with ASan
Date: Tue, 18 Nov 2025 04:12:13 -0500 [thread overview]
Message-ID: <20251118091213.GC529192@coredump.intra.peff.net> (raw)
In-Reply-To: <20251118091127.GA4175601@coredump.intra.peff.net>
Git often uses mmap() to access on-disk files. This leaves a blind spot
in our SANITIZE=address builds, since ASan does not seem to handle mmap
at all. Nor does the OS notice most out-of-bounds access, since it tends
to round up to the nearest page size (so depending on how big the map
is, you might have to overrun it by up to 4095 bytes to trigger a
segfault).
The previous commit demonstrates a memory bug that we missed. We could
have made a new test where the out-of-bounds access was much larger, or
where the mapped file ended closer to a page boundary. But the point of
running the test suite with sanitizers is to catch these problems
without having to construct specific tests.
Let's enable NO_MMAP for our ASan builds by default, which should give
us better coverage. This does increase the memory usage of Git, since
we're copying from the filesystem into heap. But the repositories in the
test suite tend to be small, so the overhead isn't really noticeable
(and ASan already has quite a performance penalty).
There are a few other known bugs that this patch will help flush out.
However, they aren't directly triggered in the test suite (yet). So
it's safe to turn this on now without breaking the test suite, which
will help us add new tests to demonstrate those other bugs as we fix
them.
Signed-off-by: Jeff King <peff@peff•net>
---
Makefile | 1 +
meson.build | 8 +++++++-
2 files changed, 8 insertions(+), 1 deletion(-)
diff --git a/Makefile b/Makefile
index 7e0f77e298..0f44268405 100644
--- a/Makefile
+++ b/Makefile
@@ -1587,6 +1587,7 @@ SANITIZE_LEAK = YesCompiledWithIt
endif
ifneq ($(filter address,$(SANITIZERS)),)
NO_REGEX = NeededForASAN
+NO_MMAP = NeededForASAN
SANITIZE_ADDRESS = YesCompiledWithIt
endif
endif
diff --git a/meson.build b/meson.build
index 1f95a06edb..f1b3615659 100644
--- a/meson.build
+++ b/meson.build
@@ -1411,12 +1411,18 @@ if host_machine.system() == 'windows'
libgit_c_args += '-DUSE_WIN32_MMAP'
else
checkfuncs += {
- 'mmap' : ['mmap.c'],
# provided by compat/mingw.c.
'unsetenv' : ['unsetenv.c'],
# provided by compat/mingw.c.
'getpagesize' : [],
}
+
+ if get_option('b_sanitize').contains('address')
+ libgit_c_args += '-DNO_MMAP'
+ libgit_sources += 'compat/mmap.c'
+ else
+ checkfuncs += { 'mmap': ['mmap.c'] }
+ endif
endif
foreach func, impls : checkfuncs
--
2.52.0.278.gadc6434dc3
next prev parent reply other threads:[~2025-11-18 9:12 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-11-12 7:55 [PATCH 0/9] asan bonanza Jeff King
2025-11-12 7:56 ` [PATCH 1/9] compat/mmap: mark unused argument in git_munmap() Jeff King
2025-11-12 8:01 ` [PATCH 2/9] pack-bitmap: handle name-hash lookups in incremental bitmaps Jeff King
2025-11-12 11:25 ` Patrick Steinhardt
2025-11-13 2:55 ` Taylor Blau
2025-11-18 8:59 ` Jeff King
2025-11-12 8:02 ` [PATCH 3/9] Makefile: turn on NO_MMAP when building with ASan Jeff King
2025-11-12 8:17 ` Collin Funk
2025-11-12 10:31 ` Jeff King
2025-11-12 20:06 ` Collin Funk
2025-11-12 11:26 ` Patrick Steinhardt
2025-11-13 3:12 ` Taylor Blau
2025-11-13 6:34 ` Patrick Steinhardt
2025-11-18 8:49 ` Jeff King
2025-11-13 16:30 ` Junio C Hamano
2025-11-14 7:00 ` Patrick Steinhardt
2025-11-15 2:13 ` Jeff King
2025-11-12 8:05 ` [PATCH 4/9] cache-tree: avoid strtol() on non-string buffer Jeff King
2025-11-12 11:26 ` Patrick Steinhardt
2025-11-13 3:09 ` Taylor Blau
2025-11-18 8:40 ` Jeff King
2025-11-18 8:38 ` Jeff King
2025-11-12 8:06 ` [PATCH 5/9] fsck: assert newline presence in fsck_ident() Jeff King
2025-11-12 8:06 ` [PATCH 6/9] fsck: avoid strcspn() " Jeff King
2025-11-12 8:06 ` [PATCH 7/9] fsck: remove redundant date timestamp check Jeff King
2025-11-12 8:10 ` [PATCH 8/9] fsck: avoid parse_timestamp() on buffer that isn't NUL-terminated Jeff King
2025-11-12 11:25 ` Patrick Steinhardt
2025-11-12 19:36 ` Junio C Hamano
2025-11-15 2:12 ` Jeff King
2025-11-12 8:10 ` [PATCH 9/9] t: enable ASan's strict_string_checks option Jeff King
2025-11-13 3:17 ` [PATCH 0/9] asan bonanza Taylor Blau
2025-11-18 9:11 ` [PATCH v2 " Jeff King
2025-11-18 9:11 ` [PATCH v2 1/9] compat/mmap: mark unused argument in git_munmap() Jeff King
2025-11-18 9:12 ` [PATCH v2 2/9] pack-bitmap: handle name-hash lookups in incremental bitmaps Jeff King
2025-11-18 9:12 ` Jeff King [this message]
2025-11-18 9:12 ` [PATCH v2 4/9] cache-tree: avoid strtol() on non-string buffer Jeff King
2025-11-18 14:30 ` Phillip Wood
2025-11-23 6:19 ` Junio C Hamano
2025-11-23 15:51 ` Phillip Wood
2025-11-23 18:06 ` Junio C Hamano
2025-11-24 22:30 ` Jeff King
2025-11-24 23:09 ` Junio C Hamano
2025-11-26 15:09 ` Jeff King
2025-11-26 17:22 ` Junio C Hamano
2025-11-30 13:13 ` [PATCH 0/4] more robust functions for parsing int from buf Jeff King
2025-11-30 13:14 ` [PATCH 1/4] parse: prefer bool to int for boolean returns Jeff King
2025-12-04 11:23 ` Patrick Steinhardt
2025-11-30 13:15 ` [PATCH 2/4] parse: add functions for parsing from non-string buffers Jeff King
2025-11-30 13:46 ` my complaints with clar Jeff King
2025-12-01 14:16 ` Phillip Wood
2025-12-04 11:09 ` Patrick Steinhardt
2025-12-05 18:30 ` Jeff King
2025-12-04 11:23 ` [PATCH 2/4] parse: add functions for parsing from non-string buffers Patrick Steinhardt
2025-12-05 16:11 ` Phillip Wood
2026-01-20 20:54 ` Junio C Hamano
2026-01-21 5:27 ` Jeff King
2025-11-30 13:15 ` [PATCH 3/4] cache-tree: use parse_int_from_buf() Jeff King
2025-11-30 13:16 ` [PATCH 4/4] fsck: use parse_unsigned_from_buf() for parsing timestamp Jeff King
2025-11-18 9:12 ` [PATCH v2 5/9] fsck: assert newline presence in fsck_ident() Jeff King
2025-11-18 9:12 ` [PATCH v2 6/9] fsck: avoid strcspn() " Jeff King
2025-11-18 9:12 ` [PATCH v2 7/9] fsck: remove redundant date timestamp check Jeff King
2025-11-18 9:12 ` [PATCH v2 8/9] fsck: avoid parse_timestamp() on buffer that isn't NUL-terminated Jeff King
2025-11-18 9:12 ` [PATCH v2 9/9] t: enable ASan's strict_string_checks option Jeff King
2025-11-23 5:49 ` [PATCH v2 0/9] asan bonanza Junio C Hamano
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