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Subject: |
chmod a-r does not fail for vfat |
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Date: |
Sat, 24 Dec 2022 02:09:57 +0100 |
chmod (GNU coreutils) 9.1 x86_64
cd /tmp
dd if=/dev/zero of=fd0 count=2880
echo 'drive a:
file="/tmp/fd0' >.mtoolsrc
mformat a:
umask 0022
udisksctl loop-setup -f fd0
udisks mount /dev/loop3p1
cd /run/media/dell/1F9D-2F6C
echo >a.txt
chmod a-r a.txt && stat a.txt
Expected: chmod: unsupported permissions
Got: -r--r--r--
This is wrong because the command chmod had failed to set the permissions as
required but it had claimed to have succeeded.
Similarly, chmod a-w and chmod o+w should succeed but chmod a+w should fail
(because the result is o+w).
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--- Begin Message ---
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Subject: |
Re: bug#60291: chmod a-r does not fail for vfat |
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Date: |
Fri, 23 Dec 2022 21:59:10 -0800 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.2 |
On 12/23/22 17:09, Krzysztof Żelechowski wrote:
chmod a-r a.txt && stat a.txt
Expected: chmod: unsupported permissions
Got: -r--r--r--
This is wrong because the command chmod had failed to set the permissions
The chmod command is doing the right thing; the problem lies elsewhere.
Run "strace chmod a-r a.txt". You should see something like
"fchmodat(AT_FDCWD, "a.txt", 0200) = 0" which means chmod told the
kernel to change a.txt's permissions to -w------- and the kernel
responded that it did so successfully.
The problem here is a squirrelly filesystem. Run "man ntfs-3g" and look
for "Access Handling and Security".
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