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Thu, 5 Nov 2026 17:44:41 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id uvqxCYnA7GrLcgAAD6G6ig (envelope-from ); Thu, 05 Nov 2026 17:44:41 +0000 Date: Thu, 5 Nov 2026 18:44:39 +0100 From: Petr Vorel To: Andrea Cervesato Cc: Linux Test Project , linux-security-module@vger.kernel.org Subject: Re: [LTP] [PATCH v3 2/2] syscalls/cma: Handle Yama ptrace_scope in tests Message-ID: <20261105174439.GA520216@pevik> Reply-To: Petr Vorel References: <20261020-fix_process_vm_writev_permissions-v3-0-1e92d7a29aef@suse.com> <20261020-fix_process_vm_writev_permissions-v3-2-1e92d7a29aef@suse.com> X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261020-fix_process_vm_writev_permissions-v3-2-1e92d7a29aef@suse.com> X-Spamd-Result: default: False [-12.50 / 50.00]; SUSE_INTERNAL_BYPASS(-9.00)[]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; MID_RHS_NOT_FQDN(0.50)[]; HAS_REPLYTO(0.30)[pvorel@suse.cz]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MIME_TRACE(0.00)[0:+]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; TO_MATCH_ENVRCPT_ALL(0.00)[]; TO_DN_SOME(0.00)[]; ARC_NA(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,suse.cz:replyto,suse.com:email]; RCPT_COUNT_THREE(0.00)[3]; MISSING_XM_UA(0.00)[]; FROM_HAS_DN(0.00)[]; RCVD_TLS_ALL(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; REPLYTO_EQ_FROM(0.00)[] X-Spam-Score: -12.50 X-Spam-Level: X-Spam-Flag: NO Hi Andrea, [ Cc Yama list ] thanks merged. Kind regards, Petr > From: Andrea Cervesato > With Yama LSM enabled, process_vm_readv() and process_vm_writev() fail > with EPERM when a sibling process accesses the target's memory. > Let the target child declare its parent as ptracer, so that mode 1 > works for unprivileged users too. Require CAP_SYS_PTRACE for mode 2 > and skip on mode 3, where access is never allowed. > Signed-off-by: Andrea Cervesato > --- > testcases/kernel/syscalls/cma/cma.h | 38 ++++++++++++++++++++++ > testcases/kernel/syscalls/cma/process_vm_readv02.c | 5 +++ > testcases/kernel/syscalls/cma/process_vm_readv03.c | 5 +++ > .../kernel/syscalls/cma/process_vm_writev02.c | 5 +++ > 4 files changed, 53 insertions(+) > diff --git a/testcases/kernel/syscalls/cma/cma.h b/testcases/kernel/syscalls/cma/cma.h > new file mode 100644 > index 000000000..6636cb5a3 > --- /dev/null > +++ b/testcases/kernel/syscalls/cma/cma.h > @@ -0,0 +1,38 @@ > +// SPDX-License-Identifier: GPL-2.0-or-later > +/* > + * Copyright (C) 2026 SUSE LLC Andrea Cervesato > + */ > + > +#ifndef CMA_H__ > +#define CMA_H__ > + > +#include > +#include "tst_test.h" > +#include "tst_capability.h" > + > +#define PTRACE_SCOPE "/proc/sys/kernel/yama/ptrace_scope" > + > +static inline void cma_check_ptrace_scope(void) > +{ > + struct tst_cap cap = TST_CAP(TST_CAP_REQ, CAP_SYS_PTRACE); > + int scope; > + > + if (access(PTRACE_SCOPE, F_OK)) > + return; > + > + SAFE_FILE_SCANF(PTRACE_SCOPE, "%d", &scope); > + > + if (scope >= 3) > + tst_brk(TCONF, "Yama ptrace_scope=%d forbids process_vm_*()", scope); > + > + if (scope == 2) > + tst_cap_action(&cap); > +} > + > +static inline void cma_allow_parent_ptracer(void) > +{ > + if (prctl(PR_SET_PTRACER, getppid(), 0, 0, 0) && errno != EINVAL) > + tst_brk(TBROK | TERRNO, "prctl(PR_SET_PTRACER)"); > +} > + > +#endif /* CMA_H__ */ > diff --git a/testcases/kernel/syscalls/cma/process_vm_readv02.c b/testcases/kernel/syscalls/cma/process_vm_readv02.c > index 1e2ac38fa..ceff77e29 100644 > --- a/testcases/kernel/syscalls/cma/process_vm_readv02.c > +++ b/testcases/kernel/syscalls/cma/process_vm_readv02.c > @@ -17,6 +17,7 @@ > #include > #include "tst_test.h" > #include "lapi/syscalls.h" > +#include "cma.h" > static uintptr_t *data_ptr; > @@ -29,6 +30,8 @@ static void child_alloc(const char *data) > tst_res(TINFO, "child 0: memory allocated and initialized"); > + cma_allow_parent_ptracer(); > + > /* wake and wait until child_invoke is done reading from our VM */ > TST_CHECKPOINT_WAKE_AND_WAIT(0); > } > @@ -64,6 +67,8 @@ static void setup(void) > /* Just a sanity check of the existence of syscall */ > tst_syscall(__NR_process_vm_readv, getpid(), NULL, 0UL, NULL, 0UL, 0UL); > + cma_check_ptrace_scope(); > + > data_ptr = SAFE_MMAP(NULL, sizeof(uintptr_t), PROT_READ | PROT_WRITE, > MAP_SHARED | MAP_ANONYMOUS, -1, 0); > } > diff --git a/testcases/kernel/syscalls/cma/process_vm_readv03.c b/testcases/kernel/syscalls/cma/process_vm_readv03.c > index 95d35c422..831f79c89 100644 > --- a/testcases/kernel/syscalls/cma/process_vm_readv03.c > +++ b/testcases/kernel/syscalls/cma/process_vm_readv03.c > @@ -20,6 +20,7 @@ > #include > #include "tst_test.h" > #include "lapi/syscalls.h" > +#include "cma.h" > #define MAX_IOVECS 1024 > @@ -80,6 +81,8 @@ static void child_alloc(const int *sizes, int nr_iovecs) > tst_res(TINFO, "child_alloc: memory allocated and initialized"); > + cma_allow_parent_ptracer(); > + > TST_CHECKPOINT_WAKE_AND_WAIT(0); > } > @@ -139,6 +142,8 @@ static void setup(void) > { > tst_syscall(__NR_process_vm_readv, getpid(), NULL, 0UL, NULL, 0UL, 0UL); > + cma_check_ptrace_scope(); > + > data_ptr = SAFE_MMAP(NULL, sizeof(void *) * MAX_IOVECS, PROT_READ | PROT_WRITE, > MAP_SHARED | MAP_ANONYMOUS, -1, 0); > } > diff --git a/testcases/kernel/syscalls/cma/process_vm_writev02.c b/testcases/kernel/syscalls/cma/process_vm_writev02.c > index 15bd66a44..78b98200f 100644 > --- a/testcases/kernel/syscalls/cma/process_vm_writev02.c > +++ b/testcases/kernel/syscalls/cma/process_vm_writev02.c > @@ -16,6 +16,7 @@ > #include > #include "tst_test.h" > #include "lapi/syscalls.h" > +#include "cma.h" > static uintptr_t *data_ptr; > static char *str_buffsize; > @@ -33,6 +34,8 @@ static void child_alloc_and_verify(int buffsize) > memset(foo, 'a', buffsize); > *data_ptr = (uintptr_t)foo; > + cma_allow_parent_ptracer(); > + > TST_CHECKPOINT_WAKE_AND_WAIT(0); > err = 0; > @@ -81,6 +84,8 @@ static void setup(void) > if (tst_parse_int(str_buffsize, &bufsize, 1, INT_MAX)) > tst_brk(TBROK, "Invalid buffer size '%s'", str_buffsize); > + cma_check_ptrace_scope(); > + > data_ptr = SAFE_MMAP(NULL, sizeof(uintptr_t), PROT_READ | PROT_WRITE, > MAP_SHARED | MAP_ANONYMOUS, -1, 0); > }