Date: Wed, 28 Nov 2018 10:50:59 +0100 From: Peter Holm <peter@holm.cc> To: Konstantin Belousov <kostikbel@gmail.com> Cc: Vladimir Kondratyev <vladimir@kondratyev.su>, current@freebsd.org Subject: Re: r340343 triggers kernel assertion if file is opened with O_BENEATH flag set through symlink Message-ID: <20181128095059.GA13602@x2.osted.lan> In-Reply-To: <20181127234617.GE2378@kib.kiev.ua> References: <d8fd4b5d-b6c7-c56e-79f3-504daceb2a51@kondratyev.su> <20181127234617.GE2378@kib.kiev.ua>
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On Wed, Nov 28, 2018 at 01:46:17AM +0200, Konstantin Belousov wrote:
> On Wed, Nov 28, 2018 at 12:54:21AM +0300, Vladimir Kondratyev wrote:
> > Following test case triggers assertion after r340343:
> >
> >
> > #include <fcntl.h>
> >
> > int
> > main(int argc, char **argv)
> > {
> > openat(open("/etc", O_RDONLY), "termcap", O_RDONLY | O_BENEATH);
> > }
> >
> > It results in:
> >
> > panic: Assertion (ndp->ni_lcf & NI_LCF_LATCH) != 0 failed at
> > /usr/src/sys/kern/vfs_lookup.c:182
> >
>
> The following should fix it. Problem was that the topping directory was
> only latched when the initial path was absolute. Since your example
> switched from the relative argument to the absolute symlink, the BENEATH
> tracker rightfully complained that there were no recorded top.
>
> I also added some asserts I used during the debugging.
>
> diff --git a/sys/kern/vfs_lookup.c b/sys/kern/vfs_lookup.c
> index 78893c4f2bd..7a80775d91d 100644
> --- a/sys/kern/vfs_lookup.c
With this patch I got a:
$ ./beneath.sh
open("a/b") succeeded
stat("a/b
panic: Assertion (ndp->ni_lcf & NI_LCF_LATCH) != 0 failed at ../../../kern/vfs_lookup.c:269
cpuid = 4
time = 1543397647
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe00c71881a0
vpanic() at vpanic+0x1a3/frame 0xfffffe00c7188200
panic() at panic+0x43/frame 0xfffffe00c7188260
namei_handle_root() at namei_handle_root+0xf7/frame 0xfffffe00c71882b0
namei() at namei+0x617/frame 0xfffffe00c71884f0
vn_open_cred() at vn_open_cred+0x526/frame 0xfffffe00c7188640
vn_open() at vn_open+0x4c/frame 0xfffffe00c7188680
kern_openat() at kern_openat+0x2e9/frame 0xfffffe00c71888e0
sys_openat() at sys_openat+0x69/frame 0xfffffe00c7188910
syscallenter() at syscallenter+0x4e3/frame 0xfffffe00c71889f0
amd64_syscall() at amd64_syscall+0x4d/frame 0xfffffe00c7188ab0
fast_syscall_common() at fast_syscall_common+0x101/frame 0xfffffe00c7188ab0
--- syscall (499, FreeBSD ELF64, sys_openat), rip = 0x8003a215a, rsp = 0x7fffffffe4f8, rbp = 0x7fffffffe5e0 ---
https://people.freebsd.org/~pho/stress/log/kostik1127.txt
- Peter
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