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Blame SOURCES/0775-journal-upload-add-asserts-that-snprintf-does-not-re.patch

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From c394463688c332199a8fcabe6f84818b57c730b3 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: Tue, 2 Oct 2018 12:46:31 +0200
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Subject: [PATCH] journal-upload: add asserts that snprintf does not return an
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 error
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LGMT complains:
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> The size argument of this snprintf call is derived from its return value,
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> which may exceed the size of the buffer and overflow.
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Let's make sure that r is non-negative. (This shouldn't occur unless the format
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string is borked, so let's just add an assert.)
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Then, let's reorder the comparison to avoid the potential overflow.
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(cherry picked from commit 91db8ed5b2e67abf738381a6ed6a05a8271498cd)
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Resolves: #1694605
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---
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 src/journal-remote/journal-upload-journal.c | 12 ++++++++----
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 1 file changed, 8 insertions(+), 4 deletions(-)
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diff --git a/src/journal-remote/journal-upload-journal.c b/src/journal-remote/journal-upload-journal.c
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index 5fd639a76a..c244a76932 100644
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--- a/src/journal-remote/journal-upload-journal.c
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+++ b/src/journal-remote/journal-upload-journal.c
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@@ -30,7 +30,8 @@ static ssize_t write_entry(char *buf, size_t size, Uploader *u) {
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                         r = snprintf(buf + pos, size - pos,
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                                      "__CURSOR=%s\n", u->current_cursor);
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-                        if (pos + r > size)
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+                        assert(r >= 0);
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+                        if ((size_t) r > size - pos)
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                                 /* not enough space */
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                                 return pos;
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@@ -54,7 +55,8 @@ static ssize_t write_entry(char *buf, size_t size, Uploader *u) {
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                         r = snprintf(buf + pos, size - pos,
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                                      "__REALTIME_TIMESTAMP="USEC_FMT"\n", realtime);
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-                        if (r + pos > size)
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+                        assert(r >= 0);
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+                        if ((size_t) r > size - pos)
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                                 /* not enough space */
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                                 return pos;
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@@ -79,7 +81,8 @@ static ssize_t write_entry(char *buf, size_t size, Uploader *u) {
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                         r = snprintf(buf + pos, size - pos,
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                                      "__MONOTONIC_TIMESTAMP="USEC_FMT"\n", monotonic);
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-                        if (r + pos > size)
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+                        assert(r >= 0);
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+                        if ((size_t) r > size - pos)
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                                 /* not enough space */
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                                 return pos;
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@@ -104,7 +107,8 @@ static ssize_t write_entry(char *buf, size_t size, Uploader *u) {
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                         r = snprintf(buf + pos, size - pos,
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                                      "_BOOT_ID=%s\n", sd_id128_to_string(boot_id, sid));
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-                        if (r + pos > size)
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+                        assert(r >= 0);
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+                        if ((size_t) r > size - pos)
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                                 /* not enough space */
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                                 return pos;
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