sched/sem_holder.c: When accessing SEM_WAITLIST, use holder's addrenv #11191
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If the semaphore is shared, the holder has put its own mmapped address
to pholder->sem. This means we must switch to the holder's address
environment when going through the held semaphores list.
A better option would be to get the kernel mapped address for the
semaphore's physical page, but that mechanism is not functional yet.
This fixes a full system crash when CONFIG_PRIORITY_INHERITANCE=y and
CONFIG_BUILD_KERNEL=y and user makes shared semaphore via:
int semfd = shm_open("sem", O_CREAT | O_RDWR, 0666);
sem_t *sem = mmap(0, sizeof(sem_t), PROT_READ | PROT_WRITE, MAP_SHARED, semfd, 0);
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xiaoxiang781216
approved these changes
Nov 15, 2023
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Summary
If the semaphore is shared, the holder has put its own mmapped address to pholder->sem. This means we must switch to the holder's address environment when going through the held semaphores list.
A better option would be to get the kernel mapped address for the semaphore's physical page, but that mechanism is not functional yet.
This fixes a full system crash when CONFIG_PRIORITY_INHERITANCE=y and CONFIG_BUILD_KERNEL=y and user makes shared semaphore via:
int semfd = shm_open("sem", O_CREAT | O_RDWR, 0666);
sem_t *sem = mmap(0, sizeof(sem_t), PROT_READ | PROT_WRITE, MAP_SHARED, semfd, 0);
Impact
Fixes system crash as mentioned above
Testing
MPFS target with kernel mode, priority inheritance and shared semaphores