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Blame SOURCES/0186-journal-fix-access-to-munmapped-memory-in-sd_journal.patch

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From 035c9e559064114e3f7ba19b593a97c4a4d4f060 Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= <zbyszek@in.waw.pl>
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Date: Sat, 28 Dec 2013 19:33:23 -0500
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Subject: [PATCH] journal: fix access to munmapped memory in
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 sd_journal_enumerate_unique
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sd_j_e_u needs to keep a reference to an object while comparing it
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with possibly duplicate objects in other files. Because the size of
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mmap cache is limited, with enough files and object to compare to,
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at some point the object being compared would be munmapped, resulting
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in a segmentation fault.
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Fix this issue by turning keep_always into a reference count that can
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be increased and decreased. Other callers which set keep_always=true
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are unmodified: their references are never released but are ignored
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when the whole file is closed, which happens at some point. keep_always
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is increased in sd_j_e_u and later on released.
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---
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 src/journal/journal-file.c   |  5 +---
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 src/journal/journal-file.h   | 24 +++++++++++++++++++
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 src/journal/journal-verify.c |  4 ----
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 src/journal/mmap-cache.c     | 57 +++++++++++++++++++++++++++++++++++---------
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 src/journal/mmap-cache.h     | 18 +++++++++++++-
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 src/journal/sd-journal.c     | 18 +++++++++++---
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 6 files changed, 103 insertions(+), 23 deletions(-)
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diff --git a/src/journal/journal-file.c b/src/journal/journal-file.c
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index 748816a..9dbd674 100644
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--- a/src/journal/journal-file.c
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+++ b/src/journal/journal-file.c
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@@ -419,7 +419,6 @@ int journal_file_move_to_object(JournalFile *f, int type, uint64_t offset, Objec
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         void *t;
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         Object *o;
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         uint64_t s;
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-        unsigned context;
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         assert(f);
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         assert(ret);
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@@ -428,10 +427,8 @@ int journal_file_move_to_object(JournalFile *f, int type, uint64_t offset, Objec
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         if (!VALID64(offset))
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                 return -EFAULT;
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-        /* One context for each type, plus one catch-all for the rest */
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-        context = type > 0 && type < _OBJECT_TYPE_MAX ? type : 0;
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-        r = journal_file_move_to(f, context, false, offset, sizeof(ObjectHeader), &t);
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+        r = journal_file_move_to(f, type_to_context(type), false, offset, sizeof(ObjectHeader), &t);
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         if (r < 0)
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                 return r;
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diff --git a/src/journal/journal-file.h b/src/journal/journal-file.h
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index 5cc2c2d..376c3d4 100644
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--- a/src/journal/journal-file.h
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+++ b/src/journal/journal-file.h
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@@ -128,6 +128,10 @@ int journal_file_open_reliably(
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 #define ALIGN64(x) (((x) + 7ULL) & ~7ULL)
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 #define VALID64(x) (((x) & 7ULL) == 0ULL)
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+/* Use six characters to cover the offsets common in smallish journal
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+ * files without adding too many zeros. */
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+#define OFSfmt "%06"PRIx64
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+
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 static inline bool VALID_REALTIME(uint64_t u) {
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         /* This considers timestamps until the year 3112 valid. That should be plenty room... */
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         return u > 0 && u < (1ULL << 55);
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@@ -197,3 +201,23 @@ int journal_file_get_cutoff_realtime_usec(JournalFile *f, usec_t *from, usec_t *
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 int journal_file_get_cutoff_monotonic_usec(JournalFile *f, sd_id128_t boot, usec_t *from, usec_t *to);
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 bool journal_file_rotate_suggested(JournalFile *f, usec_t max_file_usec);
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+
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+
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+static unsigned type_to_context(int type) {
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+        /* One context for each type, plus one catch-all for the rest */
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+        return type > 0 && type < _OBJECT_TYPE_MAX ? type : 0;
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+}
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+
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+static inline int journal_file_object_keep(JournalFile *f, Object *o, uint64_t offset) {
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+        unsigned context = type_to_context(o->object.type);
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+
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+        return mmap_cache_get(f->mmap, f->fd, f->prot, context, true,
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+                              offset, o->object.size, &f->last_stat, NULL);
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+}
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+
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+static inline int journal_file_object_release(JournalFile *f, Object *o, uint64_t offset) {
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+        unsigned context = type_to_context(o->object.type);
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+
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+        return mmap_cache_release(f->mmap, f->fd, f->prot, context,
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+                                  offset, o->object.size);
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+}
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diff --git a/src/journal/journal-verify.c b/src/journal/journal-verify.c
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index 82b0f0a..f2422ff 100644
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--- a/src/journal/journal-verify.c
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+++ b/src/journal/journal-verify.c
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@@ -34,10 +34,6 @@
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 #include "compress.h"
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 #include "fsprg.h"
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-/* Use six characters to cover the offsets common in smallish journal
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- * files without adding to many zeros. */
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-#define OFSfmt "%06"PRIx64
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-
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 static int journal_file_object_verify(JournalFile *f, uint64_t offset, Object *o) {
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         uint64_t i;
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diff --git a/src/journal/mmap-cache.c b/src/journal/mmap-cache.c
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index 03b57be..cfb26da 100644
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--- a/src/journal/mmap-cache.c
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+++ b/src/journal/mmap-cache.c
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@@ -38,7 +38,7 @@ typedef struct FileDescriptor FileDescriptor;
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 struct Window {
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         MMapCache *cache;
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-        bool keep_always;
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+        unsigned keep_always;
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         bool in_unused;
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         int prot;
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@@ -182,7 +182,7 @@ static void context_detach_window(Context *c) {
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         c->window = NULL;
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         LIST_REMOVE(Context, by_window, w->contexts, c);
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-        if (!w->contexts && !w->keep_always) {
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+        if (!w->contexts && w->keep_always == 0) {
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                 /* Not used anymore? */
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                 LIST_PREPEND(Window, unused, c->cache->unused, w);
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                 if (!c->cache->last_unused)
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@@ -357,7 +357,6 @@ static int try_context(
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         assert(m->n_ref > 0);
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         assert(fd >= 0);
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         assert(size > 0);
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-        assert(ret);
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         c = hashmap_get(m->contexts, UINT_TO_PTR(context+1));
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         if (!c)
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@@ -375,9 +374,10 @@ static int try_context(
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                 return 0;
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         }
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-        c->window->keep_always = c->window->keep_always || keep_always;
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+        c->window->keep_always += keep_always;
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-        *ret = (uint8_t*) c->window->ptr + (offset - c->window->offset);
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+        if (ret)
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+                *ret = (uint8_t*) c->window->ptr + (offset - c->window->offset);
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         return 1;
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 }
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@@ -399,7 +399,6 @@ static int find_mmap(
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         assert(m->n_ref > 0);
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         assert(fd >= 0);
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         assert(size > 0);
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-        assert(ret);
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         f = hashmap_get(m->fds, INT_TO_PTR(fd + 1));
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         if (!f)
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@@ -419,9 +418,10 @@ static int find_mmap(
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                 return -ENOMEM;
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         context_attach_window(c, w);
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-        w->keep_always = w->keep_always || keep_always;
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+        w->keep_always += keep_always;
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-        *ret = (uint8_t*) w->ptr + (offset - w->offset);
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+        if (ret)
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+                *ret = (uint8_t*) w->ptr + (offset - w->offset);
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         return 1;
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 }
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@@ -447,7 +447,6 @@ static int add_mmap(
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         assert(m->n_ref > 0);
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         assert(fd >= 0);
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         assert(size > 0);
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-        assert(ret);
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         woffset = offset & ~((uint64_t) page_size() - 1ULL);
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         wsize = size + (offset - woffset);
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@@ -517,7 +516,8 @@ static int add_mmap(
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         c->window = w;
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         LIST_PREPEND(Context, by_window, w->contexts, c);
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-        *ret = (uint8_t*) w->ptr + (offset - w->offset);
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+        if (ret)
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+                *ret = (uint8_t*) w->ptr + (offset - w->offset);
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         return 1;
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 }
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@@ -538,7 +538,6 @@ int mmap_cache_get(
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         assert(m->n_ref > 0);
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         assert(fd >= 0);
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         assert(size > 0);
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-        assert(ret);
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         /* Check whether the current context is the right one already */
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         r = try_context(m, fd, prot, context, keep_always, offset, size, ret);
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@@ -554,6 +553,42 @@ int mmap_cache_get(
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         return add_mmap(m, fd, prot, context, keep_always, offset, size, st, ret);
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 }
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+int mmap_cache_release(
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+                MMapCache *m,
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+                int fd,
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+                int prot,
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+                unsigned context,
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+                uint64_t offset,
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+                size_t size) {
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+
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+        FileDescriptor *f;
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+        Window *w;
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+
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+        assert(m);
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+        assert(m->n_ref > 0);
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+        assert(fd >= 0);
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+        assert(size > 0);
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+
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+        f = hashmap_get(m->fds, INT_TO_PTR(fd + 1));
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+        if (!f)
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+                return -EBADF;
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+
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+        assert(f->fd == fd);
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+
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+        LIST_FOREACH(by_fd, w, f->windows)
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+                if (window_matches(w, fd, prot, offset, size))
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+                        break;
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+
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+        if (!w)
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+                return -ENOENT;
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+
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+        if (w->keep_always == 0)
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+                return -ENOLCK;
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+
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+        w->keep_always -= 1;
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+        return 0;
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+}
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+
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 void mmap_cache_close_fd(MMapCache *m, int fd) {
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         FileDescriptor *f;
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diff --git a/src/journal/mmap-cache.h b/src/journal/mmap-cache.h
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index 0c42fb8..e5e3b38 100644
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--- a/src/journal/mmap-cache.h
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+++ b/src/journal/mmap-cache.h
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@@ -31,6 +31,22 @@ MMapCache* mmap_cache_new(void);
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 MMapCache* mmap_cache_ref(MMapCache *m);
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 MMapCache* mmap_cache_unref(MMapCache *m);
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-int mmap_cache_get(MMapCache *m, int fd, int prot, unsigned context, bool keep_always, uint64_t offset, size_t size, struct stat *st, void **ret);
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+int mmap_cache_get(
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+        MMapCache *m,
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+        int fd,
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+        int prot,
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+        unsigned context,
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+        bool keep_always,
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+        uint64_t offset,
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+        size_t size,
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+        struct stat *st,
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+        void **ret);
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+int mmap_cache_release(
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+        MMapCache *m,
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+        int fd,
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+        int prot,
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+        unsigned context,
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+        uint64_t offset,
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+        size_t size);
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 void mmap_cache_close_fd(MMapCache *m, int fd);
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 void mmap_cache_close_context(MMapCache *m, unsigned context);
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diff --git a/src/journal/sd-journal.c b/src/journal/sd-journal.c
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index 9676f0f..67a77e6 100644
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--- a/src/journal/sd-journal.c
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+++ b/src/journal/sd-journal.c
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@@ -2506,9 +2506,7 @@ _public_ int sd_journal_query_unique(sd_journal *j, const char *field) {
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 }
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 _public_ int sd_journal_enumerate_unique(sd_journal *j, const void **data, size_t *l) {
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-        Object *o;
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         size_t k;
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-        int r;
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         if (!j)
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                 return -EINVAL;
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@@ -2533,9 +2531,11 @@ _public_ int sd_journal_enumerate_unique(sd_journal *j, const void **data, size_
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         for (;;) {
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                 JournalFile *of;
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                 Iterator i;
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+                Object *o;
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                 const void *odata;
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                 size_t ol;
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                 bool found;
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+                int r;
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                 /* Proceed to next data object in the field's linked list */
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                 if (j->unique_offset == 0) {
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@@ -2572,8 +2572,16 @@ _public_ int sd_journal_enumerate_unique(sd_journal *j, const void **data, size_
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                         return r;
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                 /* Let's do the type check by hand, since we used 0 context above. */
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-                if (o->object.type != OBJECT_DATA)
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+                if (o->object.type != OBJECT_DATA) {
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+                        log_error("%s:offset " OFSfmt ": object has type %d, expected %d",
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+                                  j->unique_file->path, j->unique_offset,
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+                                  o->object.type, OBJECT_DATA);
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                         return -EBADMSG;
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+                }
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+
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+                r = journal_file_object_keep(j->unique_file, o, j->unique_offset);
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+                if (r < 0)
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+                        return r;
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                 r = return_data(j, j->unique_file, o, &odata, &ol);
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                 if (r < 0)
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@@ -2607,6 +2615,10 @@ _public_ int sd_journal_enumerate_unique(sd_journal *j, const void **data, size_
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                 if (found)
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                         continue;
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+                r = journal_file_object_release(j->unique_file, o, j->unique_offset);
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+                if (r < 0)
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+                        return r;
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+
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                 r = return_data(j, j->unique_file, o, data, l);
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                 if (r < 0)
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                         return r;