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Re: [PATCH] net: Fix uninitialized data usage


From: Jason Wang
Subject: Re: [PATCH] net: Fix uninitialized data usage
Date: Fri, 7 Jan 2022 10:34:41 +0800

On Fri, Jan 7, 2022 at 3:44 AM Philippe Mathieu-Daudé <f4bug@amsat.org> wrote:
>
> On 6/1/22 19:28, Patrick Venture wrote:
> > From: Peter Foley <pefoley@google.com>
> >
> > e.g.
> > 1109 15:16:20.151506 Uninitialized bytes in ioctl_common_pre at offset 0 
> > inside [0x7ffc516af9b8, 4)
> >   1109 15:16:20.151659 ==588974==WARNING: MemorySanitizer: 
> > use-of-uninitialized-value
> >   1109 15:16:20.312923     #0 0x5639b88acb21 in tap_probe_vnet_hdr_len 
> > third_party/qemu/net/tap-linux.c:183:9
> >   1109 15:16:20.312952     #1 0x5639b88afd66 in net_tap_fd_init 
> > third_party/qemu/net/tap.c:409:9
> >   1109 15:16:20.312954     #2 0x5639b88b2d1b in net_init_tap_one 
> > third_party/qemu/net/tap.c:681:19
> >   1109 15:16:20.312956     #3 0x5639b88b16a8 in net_init_tap 
> > third_party/qemu/net/tap.c:912:13
> >   1109 15:16:20.312957     #4 0x5639b8890175 in net_client_init1 
> > third_party/qemu/net/net.c:1110:9
> >   1109 15:16:20.312958     #5 0x5639b888f912 in net_client_init 
> > third_party/qemu/net/net.c:1208:15
> >   1109 15:16:20.312960     #6 0x5639b8894aa5 in net_param_nic 
> > third_party/qemu/net/net.c:1588:11
> >   1109 15:16:20.312961     #7 0x5639b900cd18 in qemu_opts_foreach 
> > third_party/qemu/util/qemu-option.c:1135:14
> >   1109 15:16:20.312962     #8 0x5639b889393c in net_init_clients 
> > third_party/qemu/net/net.c:1612:9
> >   1109 15:16:20.312964     #9 0x5639b717aaf3 in qemu_create_late_backends 
> > third_party/qemu/softmmu/vl.c:1962:5
> >   1109 15:16:20.312965     #10 0x5639b717aaf3 in qemu_init 
> > third_party/qemu/softmmu/vl.c:3694:5
> >   1109 15:16:20.312967     #11 0x5639b71083b8 in main 
> > third_party/qemu/softmmu/main.c:49:5
> >   1109 15:16:20.312968     #12 0x7f464de1d8d2 in __libc_start_main 
> > (/usr/grte/v5/lib64/libc.so.6+0x628d2)
> >   1109 15:16:20.312969     #13 0x5639b6bbd389 in _start 
> > /usr/grte/v5/debug-src/src/csu/../sysdeps/x86_64/start.S:120
> >   1109 15:16:20.312970
> >   1109 15:16:20.312975   Uninitialized value was stored to memory at
> >   1109 15:16:20.313393     #0 0x5639b88acbee in tap_probe_vnet_hdr_len 
> > third_party/qemu/net/tap-linux.c
> >   1109 15:16:20.313396     #1 0x5639b88afd66 in net_tap_fd_init 
> > third_party/qemu/net/tap.c:409:9
> >   1109 15:16:20.313398     #2 0x5639b88b2d1b in net_init_tap_one 
> > third_party/qemu/net/tap.c:681:19
> >   1109 15:16:20.313399     #3 0x5639b88b16a8 in net_init_tap 
> > third_party/qemu/net/tap.c:912:13
> >   1109 15:16:20.313400     #4 0x5639b8890175 in net_client_init1 
> > third_party/qemu/net/net.c:1110:9
> >   1109 15:16:20.313401     #5 0x5639b888f912 in net_client_init 
> > third_party/qemu/net/net.c:1208:15
> >   1109 15:16:20.313403     #6 0x5639b8894aa5 in net_param_nic 
> > third_party/qemu/net/net.c:1588:11
> >   1109 15:16:20.313404     #7 0x5639b900cd18 in qemu_opts_foreach 
> > third_party/qemu/util/qemu-option.c:1135:14
> >   1109 15:16:20.313405     #8 0x5639b889393c in net_init_clients 
> > third_party/qemu/net/net.c:1612:9
> >   1109 15:16:20.313407     #9 0x5639b717aaf3 in qemu_create_late_backends 
> > third_party/qemu/softmmu/vl.c:1962:5
> >   1109 15:16:20.313408     #10 0x5639b717aaf3 in qemu_init 
> > third_party/qemu/softmmu/vl.c:3694:5
> >   1109 15:16:20.313409     #11 0x5639b71083b8 in main 
> > third_party/qemu/softmmu/main.c:49:5
> >   1109 15:16:20.313410     #12 0x7f464de1d8d2 in __libc_start_main 
> > (/usr/grte/v5/lib64/libc.so.6+0x628d2)
> >   1109 15:16:20.313412     #13 0x5639b6bbd389 in _start 
> > /usr/grte/v5/debug-src/src/csu/../sysdeps/x86_64/start.S:120
> >   1109 15:16:20.313413
> >   1109 15:16:20.313417   Uninitialized value was stored to memory at
> >   1109 15:16:20.313791     #0 0x5639b88affbd in net_tap_fd_init 
> > third_party/qemu/net/tap.c:400:26
> >   1109 15:16:20.313826     #1 0x5639b88b2d1b in net_init_tap_one 
> > third_party/qemu/net/tap.c:681:19
> >   1109 15:16:20.313829     #2 0x5639b88b16a8 in net_init_tap 
> > third_party/qemu/net/tap.c:912:13
> >   1109 15:16:20.313831     #3 0x5639b8890175 in net_client_init1 
> > third_party/qemu/net/net.c:1110:9
> >   1109 15:16:20.313836     #4 0x5639b888f912 in net_client_init 
> > third_party/qemu/net/net.c:1208:15
> >   1109 15:16:20.313838     #5 0x5639b8894aa5 in net_param_nic 
> > third_party/qemu/net/net.c:1588:11
> >   1109 15:16:20.313839     #6 0x5639b900cd18 in qemu_opts_foreach 
> > third_party/qemu/util/qemu-option.c:1135:14
> >   1109 15:16:20.313841     #7 0x5639b889393c in net_init_clients 
> > third_party/qemu/net/net.c:1612:9
> >   1109 15:16:20.313843     #8 0x5639b717aaf3 in qemu_create_late_backends 
> > third_party/qemu/softmmu/vl.c:1962:5
> >   1109 15:16:20.313844     #9 0x5639b717aaf3 in qemu_init 
> > third_party/qemu/softmmu/vl.c:3694:5
> >   1109 15:16:20.313845     #10 0x5639b71083b8 in main 
> > third_party/qemu/softmmu/main.c:49:5
> >   1109 15:16:20.313846     #11 0x7f464de1d8d2 in __libc_start_main 
> > (/usr/grte/v5/lib64/libc.so.6+0x628d2)
> >   1109 15:16:20.313847     #12 0x5639b6bbd389 in _start 
> > /usr/grte/v5/debug-src/src/csu/../sysdeps/x86_64/start.S:120
> >   1109 15:16:20.313849
> >   1109 15:16:20.313851   Uninitialized value was created by an allocation 
> > of 'ifr' in the stack frame of function 'tap_probe_vnet_hdr'
> >   1109 15:16:20.313855     #0 0x5639b88ac680 in tap_probe_vnet_hdr 
> > third_party/qemu/net/tap-linux.c:151
> >   1109 15:16:20.313856
> >   1109 15:16:20.313878 SUMMARY: MemorySanitizer: use-of-uninitialized-value 
> > third_party/qemu/net/tap-linux.c:183:9 in tap_probe_vnet_hdr_len
> >
> > Fixes: dc69004c7d8 ("net: move tap_probe_vnet_hdr() to tap-linux.c")
> > Reviewed-by: Hao Wu <wuhaotsh@google.com>
> > Reviewed-by: Patrick Venture <venture@google.com>
> > Signed-off-by: Peter Foley <pefoley@google.com>
> > ---
> >   net/tap-linux.c | 1 +
> >   1 file changed, 1 insertion(+)
> >
> > diff --git a/net/tap-linux.c b/net/tap-linux.c
> > index 9584769740..5e70b93037 100644
> > --- a/net/tap-linux.c
> > +++ b/net/tap-linux.c
> > @@ -150,6 +150,7 @@ void tap_set_sndbuf(int fd, const NetdevTapOptions 
> > *tap, Error **errp)
> >   int tap_probe_vnet_hdr(int fd, Error **errp)
> >   {
> >       struct ifreq ifr;
> > +    memset(&ifr, 0, sizeof(ifr));
>
> Or:
>
>         struct ifreq ifr = { };
>
> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

Applied.

Thanks

>
> >
> >       if (ioctl(fd, TUNGETIFF, &ifr) != 0) {
> >           /* TUNGETIFF is available since kernel v2.6.27 */
>




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