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[daemon] fix unchecked iterator access in async start mounts #4006

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Merged
merged 1 commit into from
Apr 22, 2025
Merged

[daemon] fix unchecked iterator access in async start mounts #4006

merged 1 commit into from
Apr 22, 2025

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xmkg
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@xmkg xmkg commented Mar 26, 2025 •
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MULTI-1913

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codecov bot commented Mar 26, 2025 •
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Codecov Report

Attention: Patch coverage is 60.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 89.25%. Comparing base (e5b457f) to head (e00810d).
Report is 3607 commits behind head on main.

Files with missing lines Patch % Lines
src/daemon/daemon.cpp 60.00% 2 Missing ⚠️
Additional details and impacted files 
@@            Coverage Diff             @@
##             main    #4006      +/-   ##
==========================================
- Coverage   89.26%   89.25%   -0.02%     
==========================================
  Files         260      260              
  Lines       14693    14696       +3     
==========================================
+ Hits        13116    13117       +1     
- Misses       1577     1579       +2

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xmkg commented Mar 26, 2025

Testing this has proven to be hard since the async_wait_for_ssh_and_start_mounts_for function is a templated non-virtual private function. Also, triggering this condition depends on a synchronization failure or a race condition.

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xmkg commented Mar 26, 2025 •
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Testing this has proven to be hard since the async_wait_for_ssh_and_start_mounts_for function is a templated non-virtual private function. Also, triggering this condition depends on a synchronization failure or a race condition.

I stumbled upon this one while trying to fix the #4005, specifically by calling the monitor->on_restart() function in the VM constructor. That resulted in a crash since the operative_instances map is actively being populated during the constructor call:

multipass/src/daemon/daemon.cpp

Lines 1370 to 1371 in 13f8025

auto instance = instance_record[name] =
config->factory->create_virtual_machine(vm_desc, *config->ssh_key_provider, *this);

@xmkg
[daemon] fix unchecked iterator access in async start mounts
e00810d 
Signed-off-by: Mustafa Kemal Gilor <mustafa.gilor@canonical.com>
@xmkg xmkg force-pushed the bugfix/daemon-start-mount-unchecked-itr-access branch from 084d1e3 to e00810d Compare March 28, 2025 22:06
@ricab ricab requested a review from georgeliao April 4, 2025 15:12
@ricab ricab requested a review from Sploder12 April 14, 2025 14:53
Sploder12
Sploder12 approved these changes Apr 15, 2025
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Good catch! There is still the issue of thread safety, but at least it might not break as bad hopefully if we're lucky.

georgeliao
georgeliao approved these changes Apr 17, 2025
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Nice catch, it looks good to me.

src/daemon/daemon.cpp
@@ -3425,8 +3425,15 @@ mp::Daemon::async_wait_for_ssh_and_start_mounts_for(const std::string& name, con
fmt::memory_buffer errors;
try
{
auto it = operative_instances.find(name);
auto vm = it->second;
const auto& it = operative_instances.find(name);
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const auto& and const auto should not make a difference here since the find function returns value.

@xmkg xmkg added this pull request to the merge queue Apr 18, 2025
@github-merge-queue github-merge-queue bot removed this pull request from the merge queue due to no response for status checks Apr 18, 2025
@ricab ricab added this pull request to the merge queue Apr 21, 2025
@github-merge-queue github-merge-queue bot removed this pull request from the merge queue due to no response for status checks Apr 21, 2025
@ricab ricab added this pull request to the merge queue Apr 21, 2025
Merged via the queue into main with commit a907fc3 Apr 22, 2025
14 of 16 checks passed
@ricab ricab deleted the bugfix/daemon-start-mount-unchecked-itr-access branch April 22, 2025 03:22
@ricab ricab added this to the 1.16.0 milestone Jun 13, 2025
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@Sploder12 Sploder12 Sploder12 approved these changes

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@georgeliao georgeliao georgeliao approved these changes

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