From a54ece408582294217d5185dc40a950a3c2983ea Mon Sep 17 00:00:00 2001 From: Marek Szyprowski Date: Mon, 2 Dec 2019 12:11:14 +0100 Subject: [PATCH] fat: write: adjust data written in each partial write The code for handing file overwrite incorrectly calculated the amount of data to write when writing to the last non-cluster aligned chunk. Fix this by ensuring that no more data than the 'filesize' is written to disk. While touching min()-based calculations, change it to type-safe min_t() function. Signed-off-by: Marek Szyprowski This patch finally fixes the issue revealed by the test script from the previous patch. The correctness of the change has been also verified by the following additional test scripts: --->8-fat_test2.sh--- #!/bin/bash make sandbox_defconfig make dd if=/dev/zero of=/tmp/10M.img bs=1024 count=10k mkfs.vfat -v /tmp/10M.img cat >/tmp/cmds </tmp/model/file0001.raw yes ABC | head -c 4096 >/tmp/model/file0003.raw yes ABC | head -c 4096 >/tmp/model/file0005.raw yes DEF | head -c 7936 >/tmp/model/file0007.raw mcopy -n -i /tmp/10M.img ::file0001.raw /tmp/result mcopy -n -i /tmp/10M.img ::file0003.raw /tmp/result mcopy -n -i /tmp/10M.img ::file0005.raw /tmp/result mcopy -n -i /tmp/10M.img ::file0007.raw /tmp/result hd /tmp/10M.img if diff -urq /tmp/model /tmp/result then echo Test okay else echo Test fail fi --->8-fat_test3.sh--- #!/bin/bash make sandbox_defconfig make dd if=/dev/zero of=/tmp/10M.img bs=1024 count=10k mkfs.vfat -v /tmp/10M.img cat >/tmp/cmds </tmp/model/file0001.raw yes ABC | head -c 4096 >/tmp/model/file0003.raw yes ABC | head -c 4096 >/tmp/model/file0005.raw yes DEF | head -c 8448 >/tmp/model/file0007.raw mcopy -n -i /tmp/10M.img ::file0001.raw /tmp/result mcopy -n -i /tmp/10M.img ::file0003.raw /tmp/result mcopy -n -i /tmp/10M.img ::file0005.raw /tmp/result mcopy -n -i /tmp/10M.img ::file0007.raw /tmp/result hd /tmp/10M.img if diff -urq /tmp/model /tmp/result then echo Test okay else echo Test fail fi --->8-fat_test4.sh--- #!/bin/bash make sandbox_defconfig make dd if=/dev/zero of=/tmp/10M.img bs=1024 count=10k mkfs.vfat -v /tmp/10M.img cat >/tmp/cmds </tmp/model/file0001.raw yes ABC | head -c 4096 >/tmp/model/file0003.raw yes ABC | head -c 4096 >/tmp/model/file0005.raw yes DEF | head -c 2304 >/tmp/model/file0007.raw yes GHI | head -c 2304 >>/tmp/model/file0007.raw yes DEF | head -c 2304 >>/tmp/model/file0007.raw yes GHI | head -c 2304 >>/tmp/model/file0007.raw mcopy -n -i /tmp/10M.img ::file0001.raw /tmp/result mcopy -n -i /tmp/10M.img ::file0003.raw /tmp/result mcopy -n -i /tmp/10M.img ::file0005.raw /tmp/result mcopy -n -i /tmp/10M.img ::file0007.raw /tmp/result hd /tmp/10M.img if diff -urq /tmp/model /tmp/result then echo Test okay else echo Test fail fi --->8--- Feel free to prepare a proper sandbox/py_test based tests based on the provided test scripts. --- fs/fat/fat_write.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/fs/fat/fat_write.c b/fs/fat/fat_write.c index f946030f7d..8e4a235d7c 100644 --- a/fs/fat/fat_write.c +++ b/fs/fat/fat_write.c @@ -813,7 +813,9 @@ set_contents(fsdata *mydata, dir_entry *dentptr, loff_t pos, __u8 *buffer, offset = 0; else offset = pos - cur_pos; - wsize = min(cur_pos + actsize, filesize) - pos; + wsize = min_t(unsigned long long, actsize, filesize - cur_pos); + wsize -= offset; + if (get_set_cluster(mydata, curclust, offset, buffer, wsize, &actsize)) { printf("Error get-and-setting cluster\n"); -- 2.25.1