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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]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,suse.cz:replyto,suse.cz:email]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; FUZZY_RATELIMITED(0.00)[rspamd.com]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; TO_DN_SOME(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_TLS_ALL(0.00)[]; MISSING_XM_UA(0.00)[]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_THREE(0.00)[4]; FROM_EQ_ENVFROM(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; REPLYTO_EQ_FROM(0.00)[] X-Virus-Scanned: clamav-milter 1.0.9 at in-7.smtp.seeweb.it X-Virus-Status: Clean Subject: Re: [LTP] [PATCH] lapi/tls: reserve pre-TCB space to avoid undefined behavior in clone10.c X-BeenThere: ltp@lists.linux.it X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux Test Project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Petr Vorel Cc: ltp@lists.linux.it Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: ltp-bounces+ltp=archiver.kernel.org@lists.linux.it Sender: "ltp" Hi Changwei, > Allocate extra space before the TLS area to hold a struct pthread, ensuring > THREAD_SELF->cancelhandling is initialized to 0. This prevents undefined > behavior in __pthread_disable_asynccancel(), which is called at thread > cancellation points such as write(). > Without this, touch_tls_in_child() could get stuck in tst_res(). LGTM, but I'd prefer others had a look on it. Acked-by: Petr Vorel BTW clone10.c segfaults w/a the patch when run with more iterations: ./clone10 -i200 clone10.c:48: TINFO: Child (PID: 4271, TID: 4285): TLS value set to: 101 clone10.c:68: TPASS: Parent (PID: 4271, TID: 4271): TLS value correct: 100 clone10.c:48: TINFO: Child (PID: 4271, TID: 4286): TLS value set to: 101 clone10.c:68: TPASS: Parent (PID: 4271, TID: 4271): TLS value correct: 100 tst_test.c:1953: TBROK: Test killed by SIGSEGV! Summary: passed 15 failed 0 broken 1 skipped 0 warnings 0 Kind regards, Petr > (gdb) bt > 0 futex_wait () at ../sysdeps/nptl/futex-internal.h:141 > 1 futex_wait_simple () at ../sysdeps/nptl/futex-internal.h:172 > 2 __libc_disable_asynccancel () at ../nptl/cancellation.c:100 > 3 __GI___libc_write () at ../sysdeps/unix/sysv/linux/write.c:26 > 4 __GI___libc_write () at ../sysdeps/unix/sysv/linux/write.c:24 > 5 print_result () at tst_test.c:387 > 6 tst_vres_ () at tst_test.c:401 > 7 tst_res_ () at tst_test.c:512 > 8 touch_tls_in_child (arg=) at clone10.c:48 > 9 thread_start () at ../sysdeps/unix/sysv/linux/aarch64/clone.S:78 > Signed-off-by: Changwei Zou > --- > include/lapi/tls.h | 16 +++++++++++++--- > 1 file changed, 13 insertions(+), 3 deletions(-) > diff --git a/include/lapi/tls.h b/include/lapi/tls.h > index 468fe3086..7f2fa18a1 100644 > --- a/include/lapi/tls.h > +++ b/include/lapi/tls.h > @@ -22,6 +22,15 @@ > #define TLS_SIZE 4096 > #define TLS_ALIGN 16 > +/* > + * Space allocated large enough to hold a struct pthread. > + * > + * Zero-initialized to ensure THREAD_SELF->cancelhandling starts at 0, > + * avoiding undefined behavior (e.g., in clone10.c) in __pthread_disable_asynccancel(), > + * which is called at thread cancellation points such as write(). > + */ > +#define TLS_PRE_TCB_SIZE (TLS_ALIGN * 256) > + > #if defined(__x86_64__) > typedef struct { > void *tcb; > @@ -36,10 +45,11 @@ extern void *tls_ptr; > static inline void *allocate_tls_area(void) > { > - void *tls_area = aligned_alloc(TLS_ALIGN, TLS_SIZE); > + char *tls_area = aligned_alloc(TLS_ALIGN, TLS_PRE_TCB_SIZE + TLS_SIZE); > if (!tls_area) > tst_brk(TBROK | TERRNO, "aligned_alloc failed"); > - memset(tls_area, 0, TLS_SIZE); > + memset(tls_area, 0, TLS_PRE_TCB_SIZE + TLS_SIZE); > + tls_area += TLS_PRE_TCB_SIZE; > #if defined(__x86_64__) > tcb_t *tcb = (tcb_t *)tls_area; > @@ -59,7 +69,7 @@ static inline void free_tls(void) > { > usleep(10000); > if (tls_ptr) { > - free(tls_ptr); > + free(((char *)tls_ptr) - TLS_PRE_TCB_SIZE); > tls_ptr = NULL; > } > } -- Mailing list info: https://lists.linux.it/listinfo/ltp