[1.1] Fix error from runc run on noexec fs #3541
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kolyshkin
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When starting a new container, and the very last step of executing of a user process fails (last lines of (*linuxStandardInit).Init), it is too late to print a proper error since both the log pipe and the init pipe are closed. This is partially mitigated by using exec.LookPath() which is supposed to say whether we will be able to execute or not. Alas, it fails to do so when the binary to be executed resides on a filesystem mounted with noexec flag. A workaround would be to use access(2) with X_OK flag. Alas, it is not working when runc itself is a setuid (or setgid) binary. In this case, faccessat2(2) with AT_EACCESS can be used, but it is only available since Linux v5.8. So, use faccessat2(2) with AT_EACCESS if available. If not, fall back to access(2) for non-setuid runc, and do nothing for setuid runc (as there is nothing we can do). Note that this check if in addition to whatever exec.LookPath does. Fixes opencontainers#3520 Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com> (cherry picked from commit 957d97b) Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
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cyphar
approved these changes
Aug 2, 2022
mrunalp
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Aug 2, 2022
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Backport of #3522 to release-1.1 branch. See the original PR for details.
Draft until the original PR is merged.