In the Linux kernel, the following vulnerability has been resolved:
parisc: Fix random data corruption from exception handler
The current exception handler implementation, which assists when accessing
user space memory, may exhibit random data corruption if the compiler decides
to use a different register than the specified register %r29 (defined in
ASM_EXCEPTIONTABLE_REG) for the error code. If the compiler choose another
register, the fault handler will nevertheless store -EFAULT into %r29 and thus
trash whatever this register is used for.
Looking at the assembly I found that this happens sometimes in emulate_ldd().
To solve the issue, the easiest solution would be if it somehow is
possible to tell the fault handler which register is used to hold the error
code. Using %0 or %1 in the inline assembly is not posssible as it will show
up as e.g. %r29 (with the "%r" prefix), which the GNU assembler can not
convert to an integer.
This patch takes another, better and more flexible approach:
We extend the __ex_table (which is out of the execution path) by one 32-word.
In this word we tell the compiler to insert the assembler instruction
"or %r0,%r0,%reg", where %reg references the register which the compiler
choosed for the error return code.
In case of an access failure, the fault handler finds the __ex_table entry and
can examine the opcode. The used register is encoded in the lowest 5 bits, and
the fault handler can then store -EFAULT into this register.
Since we extend the __ex_table to 3 words we can't use the BUILDTIME_TABLE_SORT
config option any longer.
Metrics
Affected Vendors & Products
References
History
No history.
MITRE
Status: PUBLISHED
Assigner: Linux
Published: 2024-04-03T14:55:09.529Z
Updated: 2024-11-05T09:14:14.288Z
Reserved: 2024-02-19T14:20:24.158Z
Link: CVE-2024-26706
Vulnrichment
Updated: 2024-08-02T00:14:12.642Z
NVD
Status : Awaiting Analysis
Published: 2024-04-03T15:15:53.293
Modified: 2024-04-03T17:24:18.150
Link: CVE-2024-26706
Redhat