libnss-mdns: avoid race condition in postinst

PATCH Applied Phil Blundell 2 participants 2 messages Nov 14, 2011 – Nov 15, 2011

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Phil Blundell

author

2011-11-14 13:13 UTC #0 lore raw

PATCH 1/1 libnss-mdns: avoid race condition in postinst

Writing to "/tmp/nsswitch.conf" leads to a race condition if two copies of the postinst are running simultaneously. Fix this by modifying /etc/nsswitch.conf in place using sed -i. Also make the same change to the prerm for consistency although the race will not occur here in practice.

Signed-off-by Phil Blundell <[email protected]>

---
 .../libnss-mdns/libnss-mdns_0.10.bb                |    8 +++-----
 1 files changed, 3 insertions(+), 5 deletions(-)

meta/recipes-connectivity/libnss-mdns/libnss-mdns_0.10.bb +3 -5

index 5f614f8..8770714 100644
@@ -7,7 +7,7 @@ LIC_FILES_CHKSUM = "file://LICENSE;md5=2d5025d4aa3495befef8f17206a5b0a1"
 
 DEPENDS = "avahi"
 RDEPENDS_${PN} = "avahi-daemon"
-PR = "r3"
+PR = "r4"
 
 SRC_URI = "http://0pointer.de/lennart/projects/nss-mdns/nss-mdns-${PV}.tar.gz"

@@ -26,14 +26,12 @@ EXTRA_OECONF = "--libdir=${base_libdir} --disable-lynx --enable-avahi"
 # TODO: pattern based configuration update
 pkg_postinst_${PN} () {
 	cat $D/etc/nsswitch.conf | grep "hosts:\s*files dns$" > /dev/null && {
-		cat $D/etc/nsswitch.conf | sed 's/hosts:\s*files dns/& mdns4/' > /tmp/nsswitch.conf
-		mv /tmp/nsswitch.conf $D/etc/nsswitch.conf
+		sed -i 's/hosts:\s*files dns/& mdns4/' $D/etc/nsswitch.conf
 	}
 }
 
 pkg_prerm_${PN} () {
 	cat /etc/nsswitch.conf | grep "hosts:\s*files dns mdns4$" > /dev/null && {
-		cat /etc/nsswitch.conf | sed 's/\(hosts:\s*files dns\) mdns4*/\1/' > /tmp/nsswitch.conf
-		mv /tmp/nsswitch.conf /etc/nsswitch.conf
+		sed -i 's/\(hosts:\s*files dns\) mdns4*/\1/' /etc/nsswitch.conf
 	}
 }

Signature · 1 line

1.7.4.1

Richard Purdie

Applied

2011-11-15 12:27 UTC #1 lore raw

Quoted 10 lines · Phil Blundell

Writing to "/tmp/nsswitch.conf" leads to a race condition if two copies of the postinst are running simultaneously. Fix this by modifying /etc/nsswitch.conf in place using sed -i. Also make the same change to the prerm for consistency although the race will not occur here in practice.
Signed-off-by Phil Blundell <[email protected]>
---
 .../libnss-mdns/libnss-mdns_0.10.bb                |    8 +++-----
 1 files changed, 3 insertions(+), 5 deletions(-)

Merged to master, thanks.

Richard