45 lines
2.2 KiB
Diff
45 lines
2.2 KiB
Diff
From c9e0daf821b3e1e6504ca4c4e3a8b73513e28fa7 Mon Sep 17 00:00:00 2001
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From: Lennart Poettering <lennart@poettering.net>
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Date: Thu, 16 Sep 2021 12:20:09 +0200
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Subject: [PATCH] fileio: fix truncated read handling in read_virtual_file()
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We mishandled the case where the size we read from the file actually
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matched the maximum size fully. In that case we cannot really make a
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determination whether the file was fully read or only partially. In that
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case let's do another loop, so that we operate with a buffer, and
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we can detect the EOF (which will be signalled to us via a short read).
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(cherry picked from commit 00bd9a4a82ed57bc0c7f158da4564fc1eab808b4)
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Conflict:NA
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Reference:https://github.com/systemd/systemd/commit/c9e0daf821b3e1e6504ca4c4e3a8b73513e28fa7
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---
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src/basic/fileio.c | 11 ++++++++---
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1 file changed, 8 insertions(+), 3 deletions(-)
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diff --git a/src/basic/fileio.c b/src/basic/fileio.c
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index 1046e5b9b4..6c8ebe63e0 100644
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--- a/src/basic/fileio.c
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+++ b/src/basic/fileio.c
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@@ -470,9 +470,14 @@ int read_virtual_file(const char *filename, size_t max_size, char **ret_contents
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if (n <= size)
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break;
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- /* If a maximum size is specified and we already read as much, no need to try again */
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- if (max_size != SIZE_MAX && n >= max_size) {
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- n = max_size;
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+ /* If a maximum size is specified and we already read more we know the file is larger, and
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+ * can handle this as truncation case. Note that if the size of what we read equals the
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+ * maximum size then this doesn't mean truncation, the file might or might not end on that
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+ * byte. We need to rerun the loop in that case, with a larger buffer size, so that we read
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+ * at least one more byte to be able to distinguish EOF from truncation. */
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+ if (max_size != SIZE_MAX && n > max_size) {
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+ n = size; /* Make sure we never use more than what we sized the buffer for (so that
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+ * we have one free byte in it for the trailing NUL we add below).*/
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truncated = true;
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break;
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}
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--
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2.33.0
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