From: Al Viro <viro@zeniv.linux.org.uk>
To: Andreas Dilger <adilger@dilger.ca>
Cc: "Nam Cao" <namcao@linutronix.de>,
"Björn Töpel" <bjorn@kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
"Christian Brauner" <brauner@kernel.org>,
"Jan Kara" <jack@suse.cz>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
linux-riscv@lists.infradead.org, "Theodore Ts'o" <tytso@mit.edu>,
"Ext4 Developers List" <linux-ext4@vger.kernel.org>,
"Conor Dooley" <conor@kernel.org>
Subject: Re: riscv32 EXT4 splat, 6.8 regression?
Date: Sun, 14 Apr 2024 03:15:55 +0100 [thread overview]
Message-ID: <20240414021555.GQ2118490@ZenIV> (raw)
In-Reply-To: <22E65CA5-A2C0-44A3-AB01-7514916A18FC@dilger.ca>
On Sat, Apr 13, 2024 at 07:46:03PM -0600, Andreas Dilger wrote:
> As to whether the 0xfffff000 address itself is valid for riscv32 is
> outside my realm, but given that RAM is cheap it doesn't seem unlikely
> to have 4GB+ of RAM and want to use it all. The riscv32 might consider
> reserving this page address from allocation to avoid similar issues in
> other parts of the code, as is done with the NULL/0 page address.
Not a chance. *Any* page mapped there is a serious bug on any 32bit
box. Recall what ERR_PTR() is...
On any architecture the virtual addresses in range (unsigned long)-512..
(unsigned long)-1 must never resolve to valid kernel objects.
In other words, any kind of wraparound here is asking for an oops on
attempts to access the elements of buffer - kernel dereference of
(char *)0xfffff000 on a 32bit box is already a bug.
It might be getting an invalid pointer, but arithmetical overflows
are irrelevant.
next prev parent reply other threads:[~2024-04-14 2:16 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-12 14:57 riscv32 EXT4 splat, 6.8 regression? Björn Töpel
2024-04-12 15:43 ` Theodore Ts'o
2024-04-12 16:59 ` Björn Töpel
2024-04-13 4:35 ` Theodore Ts'o
2024-04-13 10:01 ` Conor Dooley
2024-04-13 14:43 ` Nam Cao
2024-04-14 0:24 ` Theodore Ts'o
2024-04-14 1:46 ` Andreas Dilger
2024-04-14 2:04 ` Theodore Ts'o
2024-04-14 2:18 ` Al Viro
2024-04-14 2:15 ` Al Viro [this message]
2024-04-14 4:16 ` Andreas Dilger
2024-04-14 14:08 ` Björn Töpel
2024-04-15 13:04 ` Christian Brauner
2024-04-15 16:04 ` Björn Töpel
2024-04-16 6:44 ` Nam Cao
2024-04-16 8:25 ` Christian Brauner
2024-04-16 11:02 ` Björn Töpel
2024-04-16 14:24 ` Mike Rapoport
2024-04-16 15:17 ` Nam Cao
2024-04-16 15:30 ` Nam Cao
2024-04-16 15:56 ` Björn Töpel
2024-04-16 16:19 ` Nam Cao
2024-04-16 16:31 ` Mike Rapoport
2024-04-16 17:00 ` Matthew Wilcox
2024-04-16 18:34 ` Mike Rapoport
2024-04-16 22:36 ` Nam Cao
2024-04-17 15:31 ` Theodore Ts'o
2024-04-17 18:06 ` Nam Cao
2024-04-17 19:34 ` Mike Rapoport
2024-04-17 22:09 ` Andreas Dilger
2024-04-18 9:17 ` Nam Cao
2024-04-16 18:05 ` Björn Töpel
2024-04-16 18:09 ` Nam Cao
2024-04-16 16:19 ` Mike Rapoport
2024-04-16 16:31 ` Matthew Wilcox
2024-04-16 18:18 ` Mike Rapoport
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