openat2: increase retry count to 128

We have seen reports of users hitting the 32 retry limit, hopefully a 4x
increase is enough to ease the pain. Ultimately, as a result of commit
02d2e4b ("gopathrs: return raw errors from openat2 retry loop") it
is practical for callers to do their own top-level infinite retry loop
if intermittent failures are unacceptable for their use-case.

Signed-off-by: Aleksa Sarai <[email protected]>

Author: cyphar

pathrs-lite/internal/fd/openat2_linux.go

@@ -32,7 +32,10 @@ func scopedLookupShouldRetry(how *unix.OpenHow, err error) bool {
 		(errors.Is(err, unix.EAGAIN) || errors.Is(err, unix.EXDEV))
 }
 
-const scopedLookupMaxRetries = 32
+// This is a fairly arbitrary limit we have just to avoid an attacker being
+// able to make us spin in an infinite retry loop -- callers can choose to
+// retry on EAGAIN if they prefer.
+const scopedLookupMaxRetries = 128
 
 // Openat2 is an [Fd]-based wrapper around unix.Openat2, but with some retry
 // logic in case of EAGAIN errors.