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authorOleg Nesterov <oleg@redhat.com>2016-03-23 00:25:33 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2016-03-23 01:36:02 +0300
commit1333ab03150478df8d6f5673a91df1e50dc6ab97 (patch)
treec522dbcaccf752623b1b2cd7a5575369add9acd1 /fs/fhandle.c
parent38739380683795354b3f0f1a1e80614e311b8617 (diff)
downloadlinux-1333ab03150478df8d6f5673a91df1e50dc6ab97.tar.xz
ptrace: change __ptrace_unlink() to clear ->ptrace under ->siglock
This test-case (simplified version of generated by syzkaller) #include <unistd.h> #include <sys/ptrace.h> #include <sys/wait.h> void test(void) { for (;;) { if (fork()) { wait(NULL); continue; } ptrace(PTRACE_SEIZE, getppid(), 0, 0); ptrace(PTRACE_INTERRUPT, getppid(), 0, 0); _exit(0); } } int main(void) { int np; for (np = 0; np < 8; ++np) if (!fork()) test(); while (wait(NULL) > 0) ; return 0; } triggers the 2nd WARN_ON_ONCE(!signr) warning in do_jobctl_trap(). The problem is that __ptrace_unlink() clears task->jobctl under siglock but task->ptrace is cleared without this lock held; this fools the "else" branch which assumes that !PT_SEIZED means PT_PTRACED. Note also that most of other PTRACE_SEIZE checks can race with detach from the exiting tracer too. Say, the callers of ptrace_trap_notify() assume that SEIZED can't go away after it was checked. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reported-by: Dmitry Vyukov <dvyukov@google.com> Cc: Tejun Heo <tj@kernel.org> Cc: syzkaller <syzkaller@googlegroups.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/fhandle.c')
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