commit 0891a31ad32d0567fbc8f73a0598925cb543d699 Author: Nick Mathewson nickm@torproject.org Date: Wed Sep 11 09:13:50 2019 -0400

madvise: tolerate EINVAL and ENOSYS when minherit fails

These errors can occur if we are built on a system with support for madvise(MADV_NOFORK) but then we are run on a system whose kernel does not support that flag.

If the error is something that we don't tolerate at all, we now log it before crashing.

Fixes bug 31696. I am calling this a bugfix on 0.4.1.1-alpha, where we actually started using the map_anon code.

This is similar to, but not the same as, the fix for #31570. --- changes/bug31696 | 5 +++++ src/lib/malloc/map_anon.c | 24 +++++++++++++++++++++--- 2 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/changes/bug31696 b/changes/bug31696 new file mode 100644 index 000000000..b9d6c4130 --- /dev/null +++ b/changes/bug31696 @@ -0,0 +1,5 @@ + o Major bugfixes (crash, Linux): + - Tolerate systems (including some Linux installations) where madvise + and/or MADV_DONTFORK are available at build-time, but not at run time. + Previously, these systems would notice a failed syscall and abort. + Fixes bug 31696; bugfix on 0.4.1.1-alpha. diff --git a/src/lib/malloc/map_anon.c b/src/lib/malloc/map_anon.c index 0f6a4150c..08b754540 100644 --- a/src/lib/malloc/map_anon.c +++ b/src/lib/malloc/map_anon.c @@ -27,6 +27,9 @@ #include <windows.h> #endif

+#include <string.h> +#include <errno.h> + /** * Macro to get the high bytes of a size_t, if there are high bytes. * Windows needs this; other operating systems define a size_t that does @@ -136,18 +139,33 @@ noinherit_mem(void *mem, size_t sz, inherit_res_t *inherit_result_out) return 0; } #endif /* defined(FLAG_ZERO) */ + #ifdef FLAG_NOINHERIT int r2 = MINHERIT(mem, sz, FLAG_NOINHERIT); if (r2 == 0) { *inherit_result_out = INHERIT_RES_DROP; + return 0; } - return r2; -#else /* !(defined(FLAG_NOINHERIT)) */ +#endif /* defined(FLAG_NOINHERIT) */ + +#if defined(FLAG_ZERO) || defined(FLAG_NOINHERIT) + /* At least one operation was tried, and neither succeeded. */ + + if (errno == ENOSYS || errno == EINVAL) { + /* Syscall not supported, or flag not supported. */ + return 0; + } else { + tor_log_err_sigsafe("Unexpected error from minherit: ", + strerror(errno), + NULL); + return -1; + } +#else (void)inherit_result_out; (void)mem; (void)sz; return 0; -#endif /* defined(FLAG_NOINHERIT) */ +#endif }

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