Jordan R Abrahams-Whitehead
2023-Dec-15 21:01 UTC
[PATCH] Allow MAP_NORESERVE in sandbox seccomp filter maps
While debugging Scudo on ChromeOS, we found that the no reserve mode immediately crashed `sshd`. We tracked it down to the sandbox-seccomp-filter. Being able to mmap with MAP_NORESERVE is useful (if not necessary) for some overcommitting allocators. During mmap calls, the flag MAP_NORESERVE is used by some allocators such as LLVM's Scudo for layout optimisation. This causes the sandbox seccomp filter for the client subprocess to die with some Scudo configurations. --- sandbox-seccomp-filter.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/sandbox-seccomp-filter.c b/sandbox-seccomp-filter.c index 23b40b643..a49c5ca99 100644 --- a/sandbox-seccomp-filter.c +++ b/sandbox-seccomp-filter.c @@ -190,9 +190,11 @@ #if defined(__NR_mmap) || defined(__NR_mmap2) # ifdef MAP_FIXED_NOREPLACE -# define SC_MMAP_FLAGS MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED|MAP_FIXED_NOREPLACE +# define SC_MMAP_FLAGS MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED \ + |MAP_NORESERVE|MAP_FIXED_NOREPLACE # else -# define SC_MMAP_FLAGS MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED +# define SC_MMAP_FLAGS MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED \ + |MAP_NORESERVE # endif /* MAP_FIXED_NOREPLACE */ /* Use this for both __NR_mmap and __NR_mmap2 variants */ # define SC_MMAP(_nr) \ -- 2.43.0.472.g3155946c3a-goog
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