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Kenton Varda <kenton@sandstorm.io> discovered that by remounting a read-only bind mount read-only in a user namespace the MNT_LOCK_READONLY bit would be cleared, allowing an unprivileged user to the remount a read-only mount read-write. Upon review of the code in remount it was discovered that the code allowed nosuid, noexec, and nodev to be cleared. It was also discovered that the code was allowing the per mount atime flags to be changed. The first naive patch to fix these issues contained the flaw that using default atime settings when remounting a filesystem could be disallowed. To avoid this problems in the future add tests to ensure unprivileged remounts are succeeding and failing at the appropriate times. Cc: stable@vger.kernel.org Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
18 lines
478 B
Makefile
18 lines
478 B
Makefile
# Makefile for mount selftests.
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all: unprivileged-remount-test
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unprivileged-remount-test: unprivileged-remount-test.c
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gcc -Wall -O2 unprivileged-remount-test.c -o unprivileged-remount-test
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# Allow specific tests to be selected.
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test_unprivileged_remount: unprivileged-remount-test
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@if [ -f /proc/self/uid_map ] ; then ./unprivileged-remount-test ; fi
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run_tests: all test_unprivileged_remount
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clean:
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rm -f unprivileged-remount-test
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.PHONY: all test_unprivileged_remount
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