4.17-stable review patch. If anyone has any objections, please let me know.
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From: Chris Novakovic chris@chrisn.me.uk
[ Upstream commit 300eec7c0a2495f771709c7642aa15f7cc148b83 ]
ic_nameservers, which stores the list of name servers discovered by ipconfig, is initialised (i.e. has all of its elements set to NONE, or 0xffffffff) by ic_nameservers_predef() in the following scenarios:
- before the "ip=" and "nfsaddrs=" kernel command line parameters are parsed (in ip_auto_config_setup()); - before autoconfiguring via DHCP or BOOTP (in ic_bootp_init()), in order to clear any values that may have been set after parsing "ip=" or "nfsaddrs=" and are no longer needed.
This means that ic_nameservers_predef() is not called when neither "ip=" nor "nfsaddrs=" is specified on the kernel command line. In this scenario, every element in ic_nameservers remains set to 0x00000000, which is indistinguishable from ANY and causes pnp_seq_show() to write the following (bogus) information to /proc/net/pnp:
#MANUAL nameserver 0.0.0.0 nameserver 0.0.0.0 nameserver 0.0.0.0
This is potentially problematic for systems that blindly link /etc/resolv.conf to /proc/net/pnp.
Ensure that ic_nameservers is also initialised when neither "ip=" nor "nfsaddrs=" are specified by calling ic_nameservers_predef() in ip_auto_config(), but only when ip_auto_config_setup() was not called earlier. This causes the following to be written to /proc/net/pnp, and is consistent with what gets written when ipconfig is configured manually but no name servers are specified on the kernel command line:
#MANUAL
Signed-off-by: Chris Novakovic chris@chrisn.me.uk Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/ipv4/ipconfig.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)
--- a/net/ipv4/ipconfig.c +++ b/net/ipv4/ipconfig.c @@ -748,6 +748,11 @@ static void __init ic_bootp_init_ext(u8 */ static inline void __init ic_bootp_init(void) { + /* Re-initialise all name servers to NONE, in case any were set via the + * "ip=" or "nfsaddrs=" kernel command line parameters: any IP addresses + * specified there will already have been decoded but are no longer + * needed + */ ic_nameservers_predef();
dev_add_pack(&bootp_packet_type); @@ -1368,6 +1373,13 @@ static int __init ip_auto_config(void) int err; unsigned int i;
+ /* Initialise all name servers to NONE (but only if the "ip=" or + * "nfsaddrs=" kernel command line parameters weren't decoded, otherwise + * we'll overwrite the IP addresses specified there) + */ + if (ic_set_manually == 0) + ic_nameservers_predef(); + #ifdef CONFIG_PROC_FS proc_create("pnp", 0444, init_net.proc_net, &pnp_seq_fops); #endif /* CONFIG_PROC_FS */ @@ -1588,6 +1600,7 @@ static int __init ip_auto_config_setup(c return 1; }
+ /* Initialise all name servers to NONE */ ic_nameservers_predef();
/* Parse string for static IP assignment. */