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| author |   Sergei Trofimovich <slyfox@gentoo.org> | 2021-03-06 09:02:32 +0000 |
|---|---|---|
| committer | Sergei Trofimovich <slyfox@gentoo.org> | 2021-03-11 08:03:04 +0000 |
| commit | f43378e14396fe5fad05bff13a73483740205881 (patch) | |
| tree | f51fd176e30ccd89922c1430fce5cd21d838eb77 | |
| parent | configure.ac: use tool-prefixed READELF (diff) | |
| download | sandbox-f43378e14396fe5fad05bff13a73483740205881.tar.gz sandbox-f43378e14396fe5fad05bff13a73483740205881.tar.bz2 sandbox-f43378e14396fe5fad05bff13a73483740205881.zip | |
libsandbox: implement vfork() via fork()
sandbox turns
vfork()/exec("/sbin/ldconfig")
into
vfork()/ptrace()+fork()/exec("/sbin/ldconfig").
It happens because "/sbin/ldconfig" is a static binary and can't be
inspected via LD_PRELOAD and sandbox falls back to fork()+ptrace()
vfork() imposes very strong requirements on what could happen between
vfork() and exec(). Above sandbox behaviour violates it.
vfork() is specified in a way that it can always can be substituted
for fork(). This change does exactly that.
Reported-by: Michał Górny
Bug: https://bugs.gentoo.org/774054
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
| -rw-r--r-- | libsandbox/symbols.h.in | 1 | ||||
| -rw-r--r-- | libsandbox/wrapper-funcs/vfork.c | 28 |
2 files changed, 29 insertions, 0 deletions
diff --git a/libsandbox/symbols.h.in b/libsandbox/symbols.h.in index bdbce08..0154c2a 100644 --- a/libsandbox/symbols.h.in +++ b/libsandbox/symbols.h.in @@ -74,3 +74,4 @@ utimensat futimesat lutimes fork +vfork diff --git a/libsandbox/wrapper-funcs/vfork.c b/libsandbox/wrapper-funcs/vfork.c new file mode 100644 index 0000000..b28e74c --- /dev/null +++ b/libsandbox/wrapper-funcs/vfork.c @@ -0,0 +1,28 @@ +/* + * vfork() wrapper. + * + * Copyright 1999-2021 Gentoo Foundation + * Licensed under the GPL-2 + */ + +/* We're only wrapping vfork() as a poor man's pthread_atfork(). That would + * require dedicated linkage against libpthread. So here we force the locks + * to a consistent state before forking. + * + * We also implement vfork() as fork() because sandbox does not meet vfork() + * requirements bet ween vfork()/exec("some-static-bianary") because we launch + * ptrace in the middle. + */ + +#define WRAPPER_ARGS_PROTO +#define WRAPPER_ARGS +#define WRAPPER_SAFE() 0 +#define WRAPPER_PRE_CHECKS() \ +({ \ + /* pthread_atfork(sb_lock, sb_unlock, sb_unlock); */ \ + sb_lock(); \ + result = sb_unwrapped_fork_DEFAULT(WRAPPER_ARGS_FULL); \ + sb_unlock(); \ + false; \ +}) +#include "__wrapper_simple.c" |