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From: Ahmad Fatoum <>
Cc: Ahmad Fatoum <>
Subject: [PATCH] commands: md: don't leak heap memory with unaligned accesses
Date: Sat, 19 Jun 2021 07:42:17 +0200	[thread overview]
Message-ID: <> (raw)

Doing unaligned near file end returns bogus results:

	barebox@Sandbox:/ md -s /dev/stickypage 4095
	00000fff: 959ff8ff                                           .

That 0x959ff8 is heap memory next to the buffer md had allocated.
Fix this by adding some zeroed padding after the buffer, so it instead

	00000fff: 000000ff                                           .

This is arguably better user experience.
This only applies to non-mappable fd's. For e.g. /dev/mem, unaligned
accesses will still be passed as-is.

Signed-off-by: Ahmad Fatoum <>
 commands/md.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/commands/md.c b/commands/md.c
index ef6a1e1bc0b1..d80c7cca0ce4 100644
--- a/commands/md.c
+++ b/commands/md.c
@@ -59,7 +59,7 @@ static int do_mem_md(int argc, char *argv[])
 		goto out;
-	buf = xmalloc(RW_BUF_SIZE);
+	buf = xzalloc(RW_BUF_SIZE + 7);
 	do {
 		now = min(size, (loff_t)RW_BUF_SIZE);

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             reply	other threads:[~2021-06-19  5:43 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-19  5:42 Ahmad Fatoum [this message]
2021-06-21  7:58 ` Sascha Hauer

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