Re: [PATCH net] net: 9p: initialize sun_server.sun_path to have addr's value only when addr is valid
From: Dominique Martinet <asmadeus@codewreck.org>
Date: 2020-10-12 07:59:30
Also in:
linux-kernel-mentees, lkml
Anant Thazhemadam wrote on Mon, Oct 12, 2020:
In p9_fd_create_unix, checking is performed to see if the addr (passed as an argument) is NULL or not. However, no check is performed to see if addr is a valid address, i.e., it doesn't entirely consist of only 0's. The initialization of sun_server.sun_path to be equal to this faulty addr value leads to an uninitialized variable, as detected by KMSAN. Checking for this (faulty addr) and returning a negative error number appropriately, resolves this issue.
I'm not sure I agree a fully zeroed address is faulty but I agree we can probably refuse it given userspace can't pass useful abstract addresses here. Just one nitpick but this is otherwise fine - good catch!
quoted hunk ↗ jump to hunk
Reported-by: syzbot+75d51fe5bf4ebe988518@syzkaller.appspotmail.com Tested-by: syzbot+75d51fe5bf4ebe988518@syzkaller.appspotmail.com Signed-off-by: Anant Thazhemadam <redacted> --- net/9p/trans_fd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c index c0762a302162..8f528e783a6c 100644 --- a/net/9p/trans_fd.c +++ b/net/9p/trans_fd.c@@ -1023,7 +1023,7 @@ p9_fd_create_unix(struct p9_client *client, const char *addr, char *args) csocket = NULL; - if (addr == NULL) + if (!addr || !strlen(addr))
Since we don't care about the actual length here, how about checking for addr[0] directly? That'll spare a strlen() call in the valid case. Well, I guess it doesn't really matter -- I'll queue this up anyway and update if you resend. Thanks, -- Dominique