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s390/cert_store: fix string length handling

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Building cert_store.o with W=1 reveals this bug:

        CC      arch/s390/kernel/cert_store.o
          arch/s390/kernel/cert_store.c:443:45: warning: ‘sprintf’ may write a terminating nul past the end of the destination [-Wformat-overflow=]
            443 |         sprintf(desc + name_len, ":%04u:%08u", vce->vce_hdr.vc_index, cs_token);
                |                                             ^
          arch/s390/kernel/cert_store.c:443:9: note: ‘sprintf’ output between 15 and 18 bytes into a destination of size 15
            443 |         sprintf(desc + name_len, ":%04u:%08u", vce->vce_hdr.vc_index, cs_token);

Fix this by using the correct maximum width for each integer component
in both buffer length calculation and format string. Also switch to
using snprintf() to guard against potential future changes to the
integer range of each component.

Fixes: 8cf57d7217 ("s390: add support for user-defined certificates")
Reported-by: Heiko Carstens <hca@linux.ibm.com>
Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
This commit is contained in:
Peter Oberparleiter 2023-09-12 16:47:32 +02:00 committed by Vasily Gorbik
parent 8d533cac92
commit 5c95bf2746
1 changed files with 4 additions and 3 deletions
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7
arch/s390/kernel/cert_store.c
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@ -432,15 +432,16 @@ static char *get_key_description(struct vcssb *vcssb, const struct vce *vce)
char *desc;
cs_token = vcssb->cs_token;
/* Description string contains "%64s:%04u:%08u\0". */
/* Description string contains "%64s:%05u:%010u\0". */
name_len = sizeof(vce->vce_hdr.vc_name);
len = name_len + 1 + 4 + 1 + 8 + 1;
len = name_len + 1 + 5 + 1 + 10 + 1;
desc = kmalloc(len, GFP_KERNEL);
if (!desc)
return NULL;
memcpy(desc, vce->vce_hdr.vc_name, name_len);
sprintf(desc + name_len, ":%04u:%08u", vce->vce_hdr.vc_index, cs_token);
snprintf(desc + name_len, len - name_len, ":%05u:%010u",
vce->vce_hdr.vc_index, cs_token);
return desc;
}