[PATCH] scripts/common: fix write_file when opened with mmap

From: Andrej Picej <andrej.picej@norik.com>
To: barebox@lists.infradead.org
Subject: [PATCH] scripts/common: fix write_file when opened with mmap
Date: Fri, 28 Jan 2022 09:00:33 +0100	[thread overview]
Message-ID: <20220128080033.167251-1-andrej.picej@norik.com> (raw)

Usage of bareboximd with -c option (Create checksum for FILE and write
it to the crc32 tag) was broken. Possibly by applying 2154de1cf36c
(bareboximd: Use mmap when possibly). The script fails with:

    $ ./scripts/bareboximd -c images/<barebox-image.img>
    Cannot write to images/<barebox-mage.img>: Bad address
    CRC: write crc token to images/<barebox-image.img> failed: -14
    Bad address

This has to do with the usage of "mmap" and "open" with O_TRUNC flag
which truncates the file length to 0. Writing to files fails with:
EFAULT (14) buf is outside your accessible address space.
Remove the truncate flag and truncate manually after writing the data.

This fixes the bareboximd script, which is now again usable with -c
option.

Signed-off-by: Anze Lesnik <anze.lesnik@norik.com>
Signed-off-by: Andrej Picej <andrej.picej@norik.com>
---
 scripts/common.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/scripts/common.c b/scripts/common.c
index 3f8dcd2d38..331988d593 100644
--- a/scripts/common.c
+++ b/scripts/common.c
@@ -107,7 +107,7 @@ int write_file(const char *filename, const void *buf, size_t size)
 	int fd, ret = 0;
 	int now;
 
-	fd = open(filename, O_WRONLY | O_TRUNC | O_CREAT,
+	fd = open(filename, O_WRONLY | O_CREAT,
 		  S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
 	if (fd < 0) {
 		fprintf(stderr, "Cannot open %s: %s\n", filename, strerror(errno));
@@ -126,6 +126,11 @@ int write_file(const char *filename, const void *buf, size_t size)
 		buf += now;
 	}
 
+	if (ftruncate(fd, now) < 0) {
+		fprintf(stderr, "Cannot truncate file: %s", strerror(errno));
+		ret = -errno;
+	}
+
 out:
 	close(fd);
 
-- 
2.25.1


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