git: 108e4f31420d - stable/15 - armv8rng: Fix an inverted test in random_rndr_read_one()

The branch stable/15 has been updated by markj:

URL: https://cgit.FreeBSD.org/src/commit/?id=108e4f31420d8c765d883afaece49a782d35943d

commit 108e4f31420d8c765d883afaece49a782d35943d
Author:     Mark Johnston <markj@FreeBSD.org>
AuthorDate: 2025-12-18 14:17:20 +0000
Commit:     Mark Johnston <markj@FreeBSD.org>
CommitDate: 2025-12-29 14:50:34 +0000

    armv8rng: Fix an inverted test in random_rndr_read_one()
    
    If we get a random number, the NZCV is set to 0b0000.  Then
    "cset %w1, ne" will test whether Z == 0 and set %w1 to 1 if so.
    More specifically, "cset %w1, ne" maps to "csinc %w1, wzr, wzr, eq",
    which stores 0 in %w1 when NZCV == 0b0100 and 1 otherwise.
    
    Thus, on a successful read we expect ret != 0, so the loop condition
    needs to be fixed.  In practice this means that we would end up trying
    to fetch entropy up to ten times in a row.  If all attempts are
    successful, the last will be returned, otherwise no entropy will be
    returned.
    
    Reported by:    Kevin Day <kevin@your.org>
    Reviewed by:    andrew
    Fixes:          9eecef052155 ("Add an Armv8 rndr random number provider")
    MFC after:      1 week
    Differential Revision:  https://reviews.freebsd.org/D54259
    
    (cherry picked from commit 93811883500b99f9f1fb4ffd6e764226d37dcfd0)
---
 sys/dev/random/armv8rng.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sys/dev/random/armv8rng.c b/sys/dev/random/armv8rng.c
index 524d80317681..9573c09aa77a 100644
--- a/sys/dev/random/armv8rng.c
+++ b/sys/dev/random/armv8rng.c
@@ -64,7 +64,7 @@ random_rndr_read_one(u_long *buf)
 		    /* 1 on success, 0 on failure */
 		    "cset	%w1, ne\n"
 		    : "=&r" (val), "=&r"(ret) :: "cc");
-	} while (ret != 0 && --loop > 0);
+	} while (ret == 0 && --loop > 0);
 
 	if (ret != 0)
 		*buf = val;