linux-kernel - [PATCH] scsi: ips: Replace kmap_atomic() with kmap_local

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20230103173131.21259-1-fmdefrancesco@gmail.com>
Date:   Tue,  3 Jan 2023 18:31:31 +0100
From:   "Fabio M. De Francesco" <fmdefrancesco@...il.com>
To:     Adaptec OEM Raid Solutions <aacraid@...rosemi.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     "Fabio M. De Francesco" <fmdefrancesco@...il.com>,
        Ira Weiny <ira.weiny@...el.com>
Subject: [PATCH] scsi: ips: Replace kmap_atomic() with kmap_local_page()

kmap_atomic() is deprecated in favor of kmap_local_page(). Therefore,
replace kmap_atomic() with kmap_local_page() in ips_is_passthru(). In
the meantime remove an unnecessary comment soon before local mapping,
align code and remove spaces (the function is short, therefore the
reviewers job won't be over-complicated by these logically unrelated
clean-ups).

kmap_atomic() is implemented like a kmap_local_page() which also disables
page-faults and preemption (the latter only for !PREEMPT_RT kernels).
The code within the mapping/unmapping in ips_is_passthru() is already
in atomic context because of a call to local_irq_save() and
kmap_local_page() can be called in atomic context too (including
interrupts).

Therefore, a mere replacement of the old API with the new one is all it
is required (i.e., there is no need to explicitly add any calls to
pagefault_disable() and/or preempt_disable()).

Suggested-by: Ira Weiny <ira.weiny@...el.com>
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@...il.com>
---
 drivers/scsi/ips.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/scsi/ips.c b/drivers/scsi/ips.c
index 16419aeec02d..bb206509265e 100644
--- a/drivers/scsi/ips.c
+++ b/drivers/scsi/ips.c
@@ -1499,17 +1499,16 @@ static int ips_is_passthru(struct scsi_cmnd *SC)
                 struct scatterlist *sg = scsi_sglist(SC);
                 char  *buffer;

-                /* kmap_atomic() ensures addressability of the user buffer.*/
                 /* local_irq_save() protects the KM_IRQ0 address slot.     */
                 local_irq_save(flags);
-                buffer = kmap_atomic(sg_page(sg)) + sg->offset;
-                if (buffer && buffer[0] == 'C' && buffer[1] == 'O' &&
-                    buffer[2] == 'P' && buffer[3] == 'P') {
-                        kunmap_atomic(buffer - sg->offset);
+		buffer = kmap_local_page(sg_page(sg)) + sg->offset;
+		if (buffer && buffer[0] == 'C' && buffer[1] == 'O' &&
+		    buffer[2] == 'P' && buffer[3] == 'P') {
+			kunmap_local(buffer);
                         local_irq_restore(flags);
                         return 1;
                 }
-                kunmap_atomic(buffer - sg->offset);
+		kunmap_local(buffer);
                 local_irq_restore(flags);
 	}
 	return 0;
-- 
2.39.0