From 574fe269f5aaf62a3ec862bf430adf91a20823bd Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Tue, 25 Jul 2023 10:09:31 -0700
Subject: [PATCH] scsi: fix legacy /proc parsing buffer overflow
The parsing code for /proc/scsi/scsi is disgusting and broken. We
should have just used 'sscanf()' or something simple like that, but the
logic may actually predate our kernel sscanf library routine for all I
know. It certainly predates both git and BK histories.
And we can't change it to be something sane like that now, because the
string matching at the start is done case-insensitively, and the
separator parsing between numbers isn't done at all, so *any* separator
will work, including a possible terminating NUL character.
This interface is root-only, and entirely for legacy use, so there is
absolutely no point in trying to tighten up the parsing. Because any
separator has traditionally worked, it's entirely possioble that people
have used random characters rather than the suggested space.
So don't bother to try to pretty it up, and let's just make a minimal
patch that can be back-ported and we can forget about this whole sorry
thing for another two decades.
Just make it at least not traverse the terminating NUL.
Reported-by: Tony Battersby <tonyb@cybernetics.com>
Link: https://lore.kernel.org/linux-scsi/b570f5fe-cb7c-863a-6ed9-f6774c219b88@cybernetics.com/
Cc: Martin K Petersen <martin.petersen@oracle.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
drivers/scsi/scsi_proc.c | 23 +++++++++++++----------
1 file changed, 13 insertions(+), 10 deletions(-)
@@ -383,6 +383,9 @@ static int scsi_remove_single_device(uint host, uint channel, uint id, uint lun)
return error;
}
+/* increment 'p', but not past the end */
+static inline char *next_p(char *p) { return p + !!*p; }
+
/**
* proc_scsi_write - handle writes to /proc/scsi/scsi
* @file: not used
@@ -431,12 +434,12 @@ static ssize_t proc_scsi_write(struct file *file, const char __user *buf,
* with "0 1 2 3" replaced by your "Host Channel Id Lun".
*/
if (!strncmp("scsi add-single-device", buffer, 22)) {
- p = buffer + 23;
+ p = buffer + 22;
- host = simple_strtoul(p, &p, 0);
- channel = simple_strtoul(p + 1, &p, 0);
- id = simple_strtoul(p + 1, &p, 0);
- lun = simple_strtoul(p + 1, &p, 0);
+ host = simple_strtoul(next_p(p), &p, 0);
+ channel = simple_strtoul(next_p(p), &p, 0);
+ id = simple_strtoul(next_p(p), &p, 0);
+ lun = simple_strtoul(next_p(p), &p, 0);
err = scsi_add_single_device(host, channel, id, lun);
@@ -445,12 +448,12 @@ static ssize_t proc_scsi_write(struct file *file, const char __user *buf,
* with "0 1 2 3" replaced by your "Host Channel Id Lun".
*/
} else if (!strncmp("scsi remove-single-device", buffer, 25)) {
- p = buffer + 26;
+ p = buffer + 25;
- host = simple_strtoul(p, &p, 0);
- channel = simple_strtoul(p + 1, &p, 0);
- id = simple_strtoul(p + 1, &p, 0);
- lun = simple_strtoul(p + 1, &p, 0);
+ host = simple_strtoul(next_p(p), &p, 0);
+ channel = simple_strtoul(next_p(p), &p, 0);
+ id = simple_strtoul(next_p(p), &p, 0);
+ lun = simple_strtoul(next_p(p), &p, 0);
err = scsi_remove_single_device(host, channel, id, lun);
}
--
2.41.0.327.gaa9166bcc0
This is the simplified version of the fix proposed by Tony Battersby for the horrid scsi /proc parsing code. It doesn't make it prettier, it just makes it less buggy. That parsing code hasn't been changed in git or BK times, so it's at least two decades since anybody touched it, and judging by how nasty it is, it's probably more than that. This is v2 with the additional bug noted by Tony hopefully fixed. Linus