ptrace: make former thread ID available via PTRACE_GETEVENTMSG after PTRACE_EVENT_EXEC stop (v.3)
Subsystems (2)
PATCH 1/1 ptrace: make former thread ID available via PTRACE_GETEVENTMSG after PTRACE_EVENT_EXEC stop (v.3)
Hi Oleg,
Please take a look at version 3 of this patch.
When multithreaded program execs under ptrace, all traced threads report WIFEXITED status, except for thread group leader and the thread which execs.
Unless tracer tracks thread group relationship between threads (which is a nontrivial task), it may fail to detect that execed thread no longer exists.
This patch allows tracer to figure out which thread performed this exec, by requesting PTRACE_GETEVENTMSG in PTRACE_EVENT_EXEC stop.
Signed-off-by Denys Vlasenko <[email protected]>
Signature · 1 line
vda
fs/exec.c +14 -4
@@ -1357,6 +1357,7 @@ int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs)unsigned int depth = bprm->recursion_depth;int try,retval;struct linux_binfmt *fmt; +pid_t uninitialized_var (old_pid ); retval =security_bprm_check (bprm);if (retval)
@@ -1370,17 +1371,26 @@ int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs)if (retval)return retval; +if (ptrace_event_enabled (current,PTRACE_EVENT_EXEC )) { +/* Need to fetch pid before load_binary changes it */ +rcu_read_lock (); + old_pid =task_pid_nr_ns (current,task_active_pid_ns (current->parent)); +rcu_read_unlock (); + } + retval = -ENOENT ;for (try=0 ; try<2 ; try++) {read_lock (&binfmt_lock);list_for_each_entry (fmt, &formats, lh) { -int (*fn)(struct linux_binprm *,struct pt_regs *) = fmt->load_binary; -if (!fn) +int (*load_binary)(struct linux_binprm *,struct pt_regs *); + + load_binary = fmt->load_binary; +if (!load_binary)continue ;if (!try_module_get (fmt->module))continue ;read_unlock (&binfmt_lock); - retval =fn (bprm, regs); + retval =load_binary (bprm, regs);/* * Restore the depth counter to its starting value * in this call, so we don't have to rely on every
@@ -1389,7 +1399,7 @@ int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs) bprm->recursion_depth = depth;if (retval >=0 ) {if (depth ==0 ) -ptrace_event (PTRACE_EVENT_EXEC ,0 ); +ptrace_event (PTRACE_EVENT_EXEC , old_pid);put_binfmt (fmt);allow_write_access (bprm->file);if (bprm->file)