Description

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

 

CVSS Version 4.0 CVSS Version 3.x CVSS Version 2.0

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CVSS 4.0 Severity and Vector Strings:

NIST: NVD

N/A

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CVSS 3.x Severity and Vector Strings:

NIST: NVD

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CVSS 2.0 Severity and Vector Strings:

NIST: NVD

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https://git.kernel.org/stable/c/23027309b099ffc4efca5477009a11dccbdae592

https://git.kernel.org/stable/c/8b1d72395635af45410b66cc4c4ab37a12c4a831

https://git.kernel.org/stable/c/ce31d79aa1f13a2345791f84935281a2c194e003

https://git.kernel.org/stable/c/fa69a8063f8b27f3c7434a0d4f464a76a62f24d2

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 a

kernel.org https://git.kernel.org/stable/c/23027309b099ffc4efca5477009a11dccbdae592 [No types assigned]

kernel.org https://git.kernel.org/stable/c/8b1d72395635af45410b66cc4c4ab37a12c4a831 [No types assigned]

kernel.org https://git.kernel.org/stable/c/ce31d79aa1f13a2345791f84935281a2c194e003 [No types assigned]

kernel.org https://git.kernel.org/stable/c/fa69a8063f8b27f3c7434a0d4f464a76a62f24d2 [No types assigned]