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| author | Juergen Gross <jgross@suse.com> | 2026-03-27 16:13:38 +0300 |
|---|---|---|
| committer | Juergen Gross <jgross@suse.com> | 2026-04-23 16:32:51 +0300 |
| commit | 27fdbab4221b375de54bf91919798d88520c6e28 (patch) | |
| tree | 07dbd4841752a8ef8145ce6bf201c13178919ab4 | |
| parent | 2e68039281932e6dc37718a1ea7cbb8e2cda42e6 (diff) | |
| download | linux-27fdbab4221b375de54bf91919798d88520c6e28.tar.xz | |
Buffer overflow in drivers/xen/sys-hypervisor.c
The build id returned by HYPERVISOR_xen_version(XENVER_build_id) is
neither NUL terminated nor a string.
The first causes a buffer overflow as sprintf in buildid_show will
read and copy till it finds a NUL.
00000000 f4 91 51 f4 dd 38 9e 9d 65 47 52 eb 10 71 db 50 |..Q..8..eGR..q.P|
00000010 b9 a8 01 42 6f 2e 32 |...Bo.2|
00000017
So use a memcpy instead of sprintf to have the correct value:
00000000 f4 91 51 f4 dd 00 9e 9d 65 47 52 eb 10 71 db 50 |..Q.....eGR..q.P|
00000010 b9 a8 01 42 |...B|
00000014
(the above have a hack to embed a zero inside and check it's
returned correctly).
This is XSA-485 / CVE-2026-31786
Fixes: 84b7625728ea ("xen: add sysfs node for hypervisor build id")
Signed-off-by: Frediano Ziglio <frediano.ziglio@citrix.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
| -rw-r--r-- | drivers/xen/sys-hypervisor.c | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/drivers/xen/sys-hypervisor.c b/drivers/xen/sys-hypervisor.c index b1bb01ba82f8..91923242a5ae 100644 --- a/drivers/xen/sys-hypervisor.c +++ b/drivers/xen/sys-hypervisor.c @@ -366,6 +366,8 @@ static ssize_t buildid_show(struct hyp_sysfs_attr *attr, char *buffer) ret = sprintf(buffer, "<denied>"); return ret; } + if (ret > PAGE_SIZE) + return -ENOSPC; buildid = kmalloc(sizeof(*buildid) + ret, GFP_KERNEL); if (!buildid) @@ -373,8 +375,10 @@ static ssize_t buildid_show(struct hyp_sysfs_attr *attr, char *buffer) buildid->len = ret; ret = HYPERVISOR_xen_version(XENVER_build_id, buildid); - if (ret > 0) - ret = sprintf(buffer, "%s", buildid->buf); + if (ret > 0) { + /* Build id is binary, not a string. */ + memcpy(buffer, buildid->buf, ret); + } kfree(buildid); return ret; |