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don't trust siginfo in rsyscall handler

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for some inexplicable reason, linux allows the sender of realtime
signals to spoof its identity. permission checks for sending signals
should limit the impact to same-user processes, but just to be safe,
we avoid trusting the siginfo structure and instead simply examine the
program state to see if we're in the middle of a legitimate rsyscall.
This commit is contained in:
Rich Felker 2011-04-03 12:20:51 -04:00
parent 6e9ed66d0d
commit c9b2d8016f
1 changed files with 2 additions and 3 deletions
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5
src/thread/pthread_create.c
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@ -80,8 +80,7 @@ static void rsyscall_handler(int sig, siginfo_t *si, void *ctx)
{
struct pthread *self = __pthread_self();
if (si->si_code > 0 || si->si_pid != self->pid ||
rs.cnt == libc.threads_minus_1) return;
if (!rs.hold || rs.cnt == libc.threads_minus_1) return;
/* Threads which have already decremented themselves from the
* thread count must not increment rs.cnt or otherwise act. */
@ -118,9 +117,9 @@ static int rsyscall(int nr, long a, long b, long c, long d, long e, long f)
rs.arg[0] = a; rs.arg[1] = b;
rs.arg[2] = c; rs.arg[3] = d;
rs.arg[4] = d; rs.arg[5] = f;
rs.hold = 1;
rs.err = 0;
rs.cnt = 0;
rs.hold = 1;
/* Dispatch signals until all threads respond */
for (i=libc.threads_minus_1; i; i--)