From: Dmitry V. Levin <ldv@altlinux.org>
Date: Thu, 19 Feb 2015 16:58:52 +0000 (+0000)
Subject: is_negated_errno: sync MAX_ERRNO with the kernel
X-Git-Tag: v4.10~99
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=fb585db562e66d3a32e810433408d6827021235c;p=strace

is_negated_errno: sync MAX_ERRNO with the kernel

Linux kernel used to guarantee that the largest errno value will not
exceed 4095, but SECCOMP_RET_ERRNO support introduced by kernel commit
v3.4-rc2-13-gacf3b2c71ed20c53dc69826683417703c2a88059 inadvertently
broke it.  The guarantee is back with kernel commit
v3.19-8275-g580c57f1076872ebc2427f898b927944ce170f2d.

* syscall.c (is_negated_errno): Set maximum errno value to 4095.
---

diff --git a/syscall.c b/syscall.c
index 2aeb0a37..156dbc8f 100644
--- a/syscall.c
+++ b/syscall.c
@@ -1584,12 +1584,8 @@ typedef unsigned long kernel_ulong_t;
 static inline bool
 is_negated_errno(kernel_ulong_t val)
 {
-	/*
-	 * Thanks to SECCOMP_RET_DATA == 0xffff, abnormally large errno
-	 * values could be easily seen when a seccomp filter is used, e.g.
-	 * BPF_STMT(BPF_RET, SECCOMP_RET_ERRNO | SECCOMP_RET_DATA)
-	 */
-	kernel_ulong_t max = -(kernel_long_t) 0x10000; /* SECCOMP_RET_DATA + 1 */
+	/* Linux kernel defines MAX_ERRNO to 4095. */
+	kernel_ulong_t max = -(kernel_long_t) 4095;
 
 #if SUPPORTED_PERSONALITIES > 1 && SIZEOF_LONG > 4
 	if (current_wordsize < sizeof(val)) {
@@ -1608,7 +1604,7 @@ is_negated_errno(kernel_ulong_t val)
 	}
 #endif
 
-	return val > max;
+	return val >= max;
 }
 
 /* Called at each syscall entry.