From 69583490856713f693291b32fc74b6d0f5992b72 Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Tue, 14 Mar 2017 17:09:22 +0800 Subject: [PATCH] file-posix: clean up max_segments buffer termination The following pattern is unsafe: char buf[32]; ret = read(fd, buf, sizeof(buf)); ... buf[ret] = 0; If read(2) returns 32 then a byte beyond the end of the buffer is zeroed. In practice this buffer overflow does not occur because the sysfs max_segments file only contains an unsigned short + '\n'. The string is always shorter than 32 bytes. Regardless, avoid this pattern because static analysis tools might complain and it could lead to real buffer overflows if copy-pasted elsewhere in the codebase. Signed-off-by: Stefan Hajnoczi Signed-off-by: Kevin Wolf --- block/file-posix.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/block/file-posix.c b/block/file-posix.c index c4c06637ef..ac6bd9fae8 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -686,7 +686,7 @@ static int hdev_get_max_segments(const struct stat *st) goto out; } do { - ret = read(fd, buf, sizeof(buf)); + ret = read(fd, buf, sizeof(buf) - 1); } while (ret == -1 && errno == EINTR); if (ret < 0) { ret = -errno; -- 2.11.0