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From 5bc590cd3ce202243cd1c3ee22104bcb4f3b6c4e Mon Sep 17 00:00:00 2001
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From: Michael Haggerty <mhagger@alum.mit.edu>
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Date: Wed, 25 Mar 2015 22:33:11 +0100
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Subject: [PATCH 2/2] resolve_ref_unsafe(): limit the number of "stat_ref"
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retries
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If there is a broken symlink where a loose reference file is expected,
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then the attempt to open() it fails with ENOENT. This error is
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misinterpreted to mean that the loose reference file itself has
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disappeared due to a race, causing the lookup to be retried. But in
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this scenario, the retries all suffer from the same problem, causing
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an infinite loop.
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So put a limit (of 5) on the number of times that the stat_ref step
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can be retried.
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Based-on-patch-by: Petr Stodulka <pstodulk@redhat.com>
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Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
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---
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refs/files-backend.c | 6 ++++--
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refs/refs-internal.h | 6 ++++++
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2 files changed, 10 insertions(+), 2 deletions(-)
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diff --git a/refs/files-backend.c b/refs/files-backend.c
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index d16feb1..245a0b5 100644
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--- a/refs/files-backend.c
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+++ b/refs/files-backend.c
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@@ -1353,6 +1353,7 @@ static int files_read_raw_ref(struct ref_store *ref_store,
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int fd;
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int ret = -1;
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int save_errno;
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+ int retries = 0;
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strbuf_reset(&sb_path);
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strbuf_git_path(&sb_path, "%s", refname);
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@@ -1390,7 +1391,8 @@ static int files_read_raw_ref(struct ref_store *ref_store,
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if (S_ISLNK(st.st_mode)) {
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strbuf_reset(&sb_contents);
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if (strbuf_readlink(&sb_contents, path, 0) < 0) {
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- if (errno == ENOENT || errno == EINVAL)
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+ if ((errno == ENOENT || errno == EINVAL) &&
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+ retries++ < MAXRETRIES)
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/* inconsistent with lstat; retry */
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goto stat_ref;
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else
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@@ -1426,7 +1428,7 @@ static int files_read_raw_ref(struct ref_store *ref_store,
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*/
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fd = open(path, O_RDONLY);
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if (fd < 0) {
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- if (errno == ENOENT)
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+ if (errno == ENOENT && retries++ < MAXRETRIES)
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/* inconsistent with lstat; retry */
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goto stat_ref;
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else
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diff --git a/refs/refs-internal.h b/refs/refs-internal.h
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index 708b260..37e6b99 100644
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--- a/refs/refs-internal.h
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+++ b/refs/refs-internal.h
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@@ -255,6 +255,12 @@ int rename_ref_available(const char *old_refname, const char *new_refname);
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/* We allow "recursive" symbolic refs. Only within reason, though */
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#define SYMREF_MAXDEPTH 5
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+/*
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+ * We allow only MAXRETRIES tries to jump on stat_ref, because of possible
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+ * infinite loop
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+ */
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+#define MAXRETRIES 5
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+
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/* Include broken references in a do_for_each_ref*() iteration: */
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#define DO_FOR_EACH_INCLUDE_BROKEN 0x01
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--
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2.5.5
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