kconfig: loop boundary condition fix

If buf[-1] just happens to hold the byte 0x0A, then nread can wrap around
to (size_t)-1, leading to invalid memory accesses.

This has caused segmentation faults when trying to build the latest
kernel snapshots for i686 in Fedora:
https://bugzilla.redhat.com/show_bug.cgi?id=1592374

Signed-off-by: Jerry James <loganjerry@gmail.com>
[alexpl@fedoraproject.org: reformatted patch for submission]
Signed-off-by: Alexander Ploumistos <alexpl@fedoraproject.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>

diff --git a/config/preprocess.c b/config/preprocess.c
index 65da87fce907ad2bc7b52adba4651dc2c32786be..5ca2df790d3cfa5f4253a33a303219aaa8fc4394 100644 (file)
--- a/config/preprocess.c
+++ b/config/preprocess.c
@@ -156,7 +156,7 @@ static char *do_shell(int argc, char *argv[])
                nread--;
 
        /* remove trailing new lines */
-       while (buf[nread - 1] == '\n')
+       while (nread > 0 && buf[nread - 1] == '\n')
                nread--;
 
        buf[nread] = 0;