zed: fix sending emails

[lnicola]

Motivation and Context

Fixes #12291

Commit 6fc3099 broke the quoting when invoking the mail program, revert part of that change

Description

I reverted that line to the old version. There might be a way to do the same thing without eval, though.

How Has This Been Tested?

I tested that notifications work again on my NAS.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Breaking change (fix or feature that would cause existing functionality to change)
• Library ABI change (libzfs, libzfs_core, libnvpair, libuutil and libzfsbootenv)
• Documentation (a change to man pages or other documentation)

Checklist:

• My code follows the OpenZFS code style requirements.
• I have updated the documentation accordingly.
• I have read the contributing document.
• I have added tests to cover my changes.
• I have run the ZFS Test Suite with this change applied.
• All commit messages are properly formatted and contain Signed-off-by.

[lnicola]

r? @nabijaczleweli

[nabijaczleweli]

What do you have ZED_EMAIL_* set to that you're seeing a difference? I would expect these to be by-definition-identical (not that I'm doubting that this is the fix, but it's certainly rather surprising).

[lnicola]

ZED_EMAIL_ADDR="me@domain.tld"
#ZED_EMAIL_PROG="mail"
#ZED_EMAIL_OPTS="-s '@SUBJECT@' @ADDRESS@"

There's a snippet in the linked issue showing what happens:

[pid 3221429] execve("/usr/bin/mail", ["mail", "-s", "'ZFS", "scrub_finish", "event", "for", "tank", "on", "nas.home'", "me@domain"], 0x55a8699eb2a0 /* 28 vars */) = 0

The argv there is bogus.

[lnicola]

Another way to show the same effect of eval (for some reason it doesn't work with command echo instead of cat):

$ strace -fe trace=execve sh -c "eval cat foo 'bar baz'" 2>&1 | rg execve
execve("/usr/bin/sh", ["sh", "-c", "eval cat foo 'bar baz'"], 0x7ffd9b787fc0 /* 62 vars */) = 0
[pid 56964] execve("/usr/bin/cat", ["cat", "foo", "bar", "baz"], 0x562353f80ed0 /* 62 vars */) = 0

$ strace -fe trace=execve sh -c "cat foo 'bar baz'" 2>&1 | rg "execve"
execve("/usr/bin/sh", ["sh", "-c", "cat foo 'bar baz'"], 0x7ffedbe6d8c0 /* 62 vars */) = 0
execve("/usr/bin/cat", ["cat", "foo", "bar baz"], 0x56338bec4bd0 /* 62 vars */) = 0

[nabijaczleweli]

Oh, right, of course, this PR is correct, yeah.

I'd extend the quote all the way to eval "${ZED_EMAIL_PROG} ${ZED_EMAIL_OPTS}", or remove it entirely, personally, since the eval "${ZED_EMAIL_PROG}" ${ZED_EMAIL_OPTS} phrasing suggests that ZED_EMAIL_PROG will be executed as argv[0], as in a normal eval-less usage, but it won't

[lnicola]

Ah, good point about the quotes, I removed them.

[lnicola]

Should I worry about the failing CI? That domain (build.zfsonlinux.org) doesn't resolve for me, but the check doesn't fail in other PRs.

[behlendorf]

@lnicola the CI failure here was unrelated, so you don't need to do anything but thanks for asking. This should be good to go.