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seccomp: Get actual errno value from failed seccomp functions

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Upon failure, a libseccomp API returns actual errno value very
rarely. Fortunately, after its commit 34bf78ab (contained in
2.5.0 release), the SCMP_FLTATR_API_SYSRAWRC attribute can be set
which makes subsequent APIs return true errno on failure.

This is especially critical when seccomp_load() fails, because
generic -ECANCELED says nothing.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
This commit is contained in:
Michal Privoznik 2022-10-26 09:30:24 +02:00 committed by Daniel P. Berrangé
parent 23f77f05f2
commit 73422d9524
2 changed files with 22 additions and 0 deletions
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9
meson.build
View File

@ -636,10 +636,16 @@ if vmnet.found() and not cc.has_header_symbol('vmnet/vmnet.h',
endif
seccomp = not_found
seccomp_has_sysrawrc = false
if not get_option('seccomp').auto() or have_system or have_tools
seccomp = dependency('libseccomp', version: '>=2.3.0',
required: get_option('seccomp'),
method: 'pkg-config', kwargs: static_kwargs)
if seccomp.found()
seccomp_has_sysrawrc = cc.has_header_symbol('seccomp.h',
'SCMP_FLTATR_API_SYSRAWRC',
dependencies: seccomp)
endif
endif
libcap_ng = not_found
@ -1849,6 +1855,9 @@ config_host_data.set('CONFIG_RDMA', rdma.found())
config_host_data.set('CONFIG_SDL', sdl.found())
config_host_data.set('CONFIG_SDL_IMAGE', sdl_image.found())
config_host_data.set('CONFIG_SECCOMP', seccomp.found())
if seccomp.found()
config_host_data.set('CONFIG_SECCOMP_SYSRAWRC', seccomp_has_sysrawrc)
endif
config_host_data.set('CONFIG_SNAPPY', snappy.found())
config_host_data.set('CONFIG_TPM', have_tpm)
config_host_data.set('CONFIG_USB_LIBUSB', libusb.found())

13
softmmu/qemu-seccomp.c
View File

@ -312,6 +312,19 @@ static int seccomp_start(uint32_t seccomp_opts, Error **errp)
goto seccomp_return;
}
#if defined(CONFIG_SECCOMP_SYSRAWRC)
/*
* This must be the first seccomp_attr_set() call to have full
* error propagation from subsequent seccomp APIs.
*/
rc = seccomp_attr_set(ctx, SCMP_FLTATR_API_SYSRAWRC, 1);
if (rc != 0) {
error_setg_errno(errp, -rc,
"failed to set seccomp rawrc attribute");
goto seccomp_return;
}
#endif
rc = seccomp_attr_set(ctx, SCMP_FLTATR_CTL_TSYNC, 1);
if (rc != 0) {
error_setg_errno(errp, -rc,