| Message ID | 20180905161841.10904-1-jcmvbkbc@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] linux-user: do setrlimit selectively | expand |
On 5 September 2018 at 17:18, Max Filippov <jcmvbkbc@gmail.com> wrote: > setrlimit guest calls that affect memory resources > (RLIMIT_{AS,DATA,STACK}) may interfere with QEMU internal memory > management. They may result in QEMU lockup because mprotect call in > page_unprotect would fail with ENOMEM error code, causing infinite loop > of SIGSEGV. E.g. it happens when running libstdc++ testsuite for xtensa > target on x86_64 host. > > Don't call host setrlimit for memory-related resources. > > Signed-off-by: Max Filippov <jcmvbkbc@gmail.com> > --- > Changes v1->v2: > - don't limit change to 32-bit guest on 64-bit host case > > linux-user/syscall.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/linux-user/syscall.c b/linux-user/syscall.c > index bb42a225eb58..a9cace49dad8 100644 > --- a/linux-user/syscall.c > +++ b/linux-user/syscall.c > @@ -9275,7 +9275,13 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1, > rlim.rlim_cur = target_to_host_rlim(target_rlim->rlim_cur); > rlim.rlim_max = target_to_host_rlim(target_rlim->rlim_max); > unlock_user_struct(target_rlim, arg2, 0); > - ret = get_errno(setrlimit(resource, &rlim)); > + if (resource != RLIMIT_AS && > + resource != RLIMIT_DATA && > + resource != RLIMIT_STACK) { > + return get_errno(setrlimit(resource, &rlim)); > + } else { > + return 0; > + } > } Can we have a comment here explaining why we don't enforce these limits? Something like /* * If we just passed through resource limit settings for memory then * they would also apply to QEMU's own allocations, and QEMU will * crash or hang or die if its allocations fail. Ideally we would * track the guest allocations in QEMU and apply the limits ourselves. * For now, just tell the guest the call succeeded but don't actually * limit anything. */ Otherwise Reviewed-by: Peter Maydell <peter.maydell@linaro.org> thanks -- PMM
diff --git a/linux-user/syscall.c b/linux-user/syscall.c index bb42a225eb58..a9cace49dad8 100644 --- a/linux-user/syscall.c +++ b/linux-user/syscall.c @@ -9275,7 +9275,13 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1, rlim.rlim_cur = target_to_host_rlim(target_rlim->rlim_cur); rlim.rlim_max = target_to_host_rlim(target_rlim->rlim_max); unlock_user_struct(target_rlim, arg2, 0); - ret = get_errno(setrlimit(resource, &rlim)); + if (resource != RLIMIT_AS && + resource != RLIMIT_DATA && + resource != RLIMIT_STACK) { + return get_errno(setrlimit(resource, &rlim)); + } else { + return 0; + } } break; #endif
setrlimit guest calls that affect memory resources (RLIMIT_{AS,DATA,STACK}) may interfere with QEMU internal memory management. They may result in QEMU lockup because mprotect call in page_unprotect would fail with ENOMEM error code, causing infinite loop of SIGSEGV. E.g. it happens when running libstdc++ testsuite for xtensa target on x86_64 host. Don't call host setrlimit for memory-related resources. Signed-off-by: Max Filippov <jcmvbkbc@gmail.com> --- Changes v1->v2: - don't limit change to 32-bit guest on 64-bit host case linux-user/syscall.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)