[PATCH v3 1/1] fsmonitor: don't fill bitmap with entries to be removed
From: William Baker <William.Baker@microsoft.com>
While doing some testing with fsmonitor enabled I found that git commands would segfault after staging and unstaging an untracked file. Looking at the crash it appeared that fsmonitor_ewah_callback was attempting to adjust bits beyond the bounds of the index cache.
Digging into how this could happen it became clear that the fsmonitor extension must have been written with more bits than there were entries in the index. The root cause ended up being that fill_fsmonitor_bitmap was populating fsmonitor_dirty with bits for all entries in the index, even those that had been marked for removal.
To solve this problem fill_fsmonitor_bitmap has been updated to skip entries with the the CE_REMOVE flag set. With this change the bits written for the fsmonitor extension will be consistent with the index entries written by do_write_index. Additionally, BUG checks have been added to detect if the number of bits in fsmonitor_dirty should ever exceed the number of entries in the index again.
Another option that was considered was moving the call to fill_fsmonitor_bitmap closer to where the index is written (and where the fsmonitor extension itself is written). However, that did not work as the fsmonitor_dirty bitmap must be filled before the index is split during writing.
Signed-off-by: William Baker <William.Baker@microsoft.com>
---
fsmonitor.c | 29 ++++++++++++++++++++++++-----
t/t7519-status-fsmonitor.sh | 17 +++++++++++++++++
t/t7519/fsmonitor-env | 24 ++++++++++++++++++++++++
3 files changed, 65 insertions(+), 5 deletions(-)
create mode 100755 t/t7519/fsmonitor-env
Show changes to 3 files +65 −5
fsmonitor.c, t/t7519-status-fsmonitor.sh, t/t7519/fsmonitor-env
diff --git a/fsmonitor.c b/fsmonitor.c
index 231e83a94d..7e27839278 100644
--- a/fsmonitor.c
+++ b/fsmonitor.c
@@ -14,8 +14,13 @@ struct trace_key trace_fsmonitor = TRACE_KEY_INIT(FSMONITOR);
static void fsmonitor_ewah_callback(size_t pos, void *is)
{
struct index_state *istate = (struct index_state *)is;
- struct cache_entry *ce = istate->cache[pos];
+ struct cache_entry *ce;
+
+ if (pos >= istate->cache_nr)
+ BUG("fsmonitor_dirty has more entries than the index (%"PRIuMAX" >= %u)",
+ (uintmax_t)pos, istate->cache_nr);
+ ce = istate->cache[pos];
ce->ce_flags &= ~CE_FSMONITOR_VALID;
}
@@ -50,17 +55,24 @@ int read_fsmonitor_extension(struct index_state *istate, const void *data,
}
istate->fsmonitor_dirty = fsmonitor_dirty;
+ if (istate->fsmonitor_dirty->bit_size > istate->cache_nr)
+ BUG("fsmonitor_dirty has more entries than the index (%"PRIuMAX" > %u)",
+ (uintmax_t)istate->fsmonitor_dirty->bit_size, istate->cache_nr);
+
trace_printf_key(&trace_fsmonitor, "read fsmonitor extension successful");
return 0;
}
void fill_fsmonitor_bitmap(struct index_state *istate)
{
- unsigned int i;
+ unsigned int i, skipped = 0;
istate->fsmonitor_dirty = ewah_new();
- for (i = 0; i < istate->cache_nr; i++)
- if (!(istate->cache[i]->ce_flags & CE_FSMONITOR_VALID))
- ewah_set(istate->fsmonitor_dirty, i);
+ for (i = 0; i < istate->cache_nr; i++) {
+ if (istate->cache[i]->ce_flags & CE_REMOVE)
+ skipped++;
+ else if (!(istate->cache[i]->ce_flags & CE_FSMONITOR_VALID))
+ ewah_set(istate->fsmonitor_dirty, i - skipped);
+ }
}
void write_fsmonitor_extension(struct strbuf *sb, struct index_state *istate)
@@ -71,6 +83,10 @@ void write_fsmonitor_extension(struct strbuf *sb, struct index_state *istate)
uint32_t ewah_size = 0;
int fixup = 0;
+ if (istate->fsmonitor_dirty->bit_size > istate->cache_nr)
+ BUG("fsmonitor_dirty has more entries than the index (%"PRIuMAX" > %u)",
+ (uintmax_t)istate->fsmonitor_dirty->bit_size, istate->cache_nr);
+
put_be32(&hdr_version, INDEX_EXTENSION_VERSION);
strbuf_add(sb, &hdr_version, sizeof(uint32_t));
@@ -236,6 +252,9 @@ void tweak_fsmonitor(struct index_state *istate)
}
/* Mark all previously saved entries as dirty */
+ if (istate->fsmonitor_dirty->bit_size > istate->cache_nr)
+ BUG("fsmonitor_dirty has more entries than the index (%"PRIuMAX" > %u)",
+ (uintmax_t)istate->fsmonitor_dirty->bit_size, istate->cache_nr);
ewah_each_bit(istate->fsmonitor_dirty, fsmonitor_ewah_callback, istate);
/* Now mark the untracked cache for fsmonitor usage */
diff --git a/t/t7519-status-fsmonitor.sh b/t/t7519-status-fsmonitor.sh
index 81a375fa0f..af3f9951fa 100755
--- a/t/t7519-status-fsmonitor.sh
+++ b/t/t7519-status-fsmonitor.sh
@@ -354,4 +354,21 @@ test_expect_success 'discard_index() also discards fsmonitor info' '
test_cmp expect actual
'
+# Test staging/unstaging files that appear at the end of the index. Test
+# file names begin with 'z' so that they are sorted to the end of the index.
+test_expect_success 'status succeeds after staging/unstaging ' '
+ test_create_repo fsmonitor-stage-unstage &&
+ (
+ cd fsmonitor-stage-unstage &&
+ test_commit initial &&
+ git update-index --fsmonitor &&
+ removed=$(test_seq 1 100 | sed "s/^/z/") &&
+ touch $removed &&
+ git add $removed &&
+ git config core.fsmonitor "$TEST_DIRECTORY/t7519/fsmonitor-env" &&
+ FSMONITOR_LIST="$removed" git restore -S $removed &&
+ FSMONITOR_LIST="$removed" git status
+ )
+'
+
test_done
diff --git a/t/t7519/fsmonitor-env b/t/t7519/fsmonitor-env
new file mode 100755
index 0000000000..8f1f7ab164
--- /dev/null
+++ b/t/t7519/fsmonitor-env
@@ -0,0 +1,24 @@
+#!/bin/sh
+#
+# An test hook script to integrate with git to test fsmonitor.
+#
+# The hook is passed a version (currently 1) and a time in nanoseconds
+# formatted as a string and outputs to stdout all files that have been
+# modified since the given time. Paths must be relative to the root of
+# the working tree and separated by a single NUL.
+#
+#echo "$0 $*" >&2
+
+if test "$#" -ne 2
+then
+ echo "$0: exactly 2 arguments expected" >&2
+ exit 2
+fi
+
+if test "$1" != 1
+then
+ echo "Unsupported core.fsmonitor hook version." >&2
+ exit 1
+fi
+
+printf '%s\n' $FSMONITOR_LIST
--
gitgitgadget
