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randr: avoid integer truncation in length check of ProcRRChange*Property 

Affected are ProcRRChangeProviderProperty and ProcRRChangeOutputProperty.
See also xserver@8f454b79 where this same bug was fixed for the core
protocol and XI.

This fixes an OOB read and the resulting information disclosure.

Length calculation for the request was clipped to a 32-bit integer. With
the correct stuff->nUnits value the expected request size was
truncated, passing the REQUEST_FIXED_SIZE check.

The server then proceeded with reading at least stuff->num_items bytes
(depending on stuff->format) from the request and stuffing whatever it
finds into the property. In the process it would also allocate at least
stuff->nUnits bytes, i.e. 4GB.

CVE-2023-6478, ZDI-CAN-22561

This vulnerability was discovered by:
Jan-Niklas Sohn working with Trend Micro Zero Day Initiative
This commit is contained in:
Peter Hutterer 2023-11-27 16:27:49 +10:00
parent 456b0e86bb
commit 14f480010a
2 changed files with 2 additions and 2 deletions
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2
randr/rrproperty.c
View File

@ -530,7 +530,7 @@ ProcRRChangeOutputProperty(ClientPtr client)
char format, mode;
unsigned long len;
int sizeInBytes;
int totalSize;
uint64_t totalSize;
int err;
REQUEST_AT_LEAST_SIZE(xRRChangeOutputPropertyReq);

2
randr/rrproviderproperty.c
View File

@ -498,7 +498,7 @@ ProcRRChangeProviderProperty(ClientPtr client)
char format, mode;
unsigned long len;
int sizeInBytes;
int totalSize;
uint64_t totalSize;
int err;
REQUEST_AT_LEAST_SIZE(xRRChangeProviderPropertyReq);