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s390/pci: Fix leak of uninitialized kernel data in SCLP report

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While report_error_write() checks that the provided buffer is at least
as large as the header struct, but not that it is large enough to
contain the report with the length claimed by report->length. If
user-space provides a short buffer, meaning a larger report->length than
the actually written payload, up to around 4K of kernel data from past
the kmalloc(len + 1) sized buffer allocated in kernfs_fop_write_iter()
will leak into the SCLP report.

However, as the entity processing the SCLP is privileged and able to
access at least the page including the report, this does not leak data
that entity could not access but it is still an out of bounds read and
a malformed error report that should be rejected.

Fixes: 368704a65b ("s390/pci: add report_error attribute")
Cc: stable@vger.kernel.org
Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
Reviewed-by: Benjamin Block <bblock@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
This commit is contained in:
Niklas Schnelle 2026-08-06 11:43:39 +02:00 committed by Heiko Carstens
parent 37f61b71cb
commit 8ac60ae2a3
1 changed files with 3 additions and 0 deletions
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3
arch/s390/pci/pci_sysfs.c
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@ -153,6 +153,9 @@ static ssize_t report_error_write(struct file *filp, struct kobject *kobj,
if (off || (count < sizeof(*report)))
return -EINVAL;
if (count < (report->length + sizeof(*report)))
return -EINVAL;
ret = sclp_pci_report(report, zdev->fh, zdev->fid);
return ret ? ret : count;