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elf_core_dump: use rcu_read_lock() to access ->real_parent
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In theory it is not safe to dereference ->parent/real_parent without
tasklist or rcu lock, we can race with re-parenting.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Roland McGrath <roland@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@oleg-nesterov @torvalds
oleg-nesterov authored and torvalds committed Jun 18, 2009
1 parent 72a1de3 commit 3b34fc5
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Showing 2 changed files with 12 additions and 4 deletions.
8 changes: 6 additions & 2 deletions fs/binfmt_elf.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1340,8 +1340,10 @@ static void fill_prstatus(struct elf_prstatus *prstatus,
prstatus->pr_info.si_signo = prstatus->pr_cursig = signr;
prstatus->pr_sigpend = p->pending.signal.sig[0];
prstatus->pr_sighold = p->blocked.sig[0];
rcu_read_lock();
prstatus->pr_ppid = task_pid_vnr(rcu_dereference(p->real_parent));
rcu_read_unlock();
prstatus->pr_pid = task_pid_vnr(p);
prstatus->pr_ppid = task_pid_vnr(p->real_parent);
prstatus->pr_pgrp = task_pgrp_vnr(p);
prstatus->pr_sid = task_session_vnr(p);
if (thread_group_leader(p)) {
Expand Down Expand Up @@ -1382,8 +1384,10 @@ static int fill_psinfo(struct elf_prpsinfo *psinfo, struct task_struct *p,
psinfo->pr_psargs[i] = ' ';
psinfo->pr_psargs[len] = 0;

rcu_read_lock();
psinfo->pr_ppid = task_pid_vnr(rcu_dereference(p->real_parent));
rcu_read_unlock();
psinfo->pr_pid = task_pid_vnr(p);
psinfo->pr_ppid = task_pid_vnr(p->real_parent);
psinfo->pr_pgrp = task_pgrp_vnr(p);
psinfo->pr_sid = task_session_vnr(p);

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8 changes: 6 additions & 2 deletions fs/binfmt_elf_fdpic.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1387,8 +1387,10 @@ static void fill_prstatus(struct elf_prstatus *prstatus,
prstatus->pr_info.si_signo = prstatus->pr_cursig = signr;
prstatus->pr_sigpend = p->pending.signal.sig[0];
prstatus->pr_sighold = p->blocked.sig[0];
rcu_read_lock();
prstatus->pr_ppid = task_pid_vnr(rcu_dereference(p->real_parent));
rcu_read_unlock();
prstatus->pr_pid = task_pid_vnr(p);
prstatus->pr_ppid = task_pid_vnr(p->real_parent);
prstatus->pr_pgrp = task_pgrp_vnr(p);
prstatus->pr_sid = task_session_vnr(p);
if (thread_group_leader(p)) {
Expand Down Expand Up @@ -1432,8 +1434,10 @@ static int fill_psinfo(struct elf_prpsinfo *psinfo, struct task_struct *p,
psinfo->pr_psargs[i] = ' ';
psinfo->pr_psargs[len] = 0;

rcu_read_lock();
psinfo->pr_ppid = task_pid_vnr(rcu_dereference(p->real_parent));
rcu_read_unlock();
psinfo->pr_pid = task_pid_vnr(p);
psinfo->pr_ppid = task_pid_vnr(p->real_parent);
psinfo->pr_pgrp = task_pgrp_vnr(p);
psinfo->pr_sid = task_session_vnr(p);

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