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um: Fix kernel mode fault condition

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We have to exclude memory locations <= PAGE_SIZE from
the condition and let the kernel mode fault path catch it.
Otherwise a kernel NULL pointer exception will be reported
as a kernel user space access.

Fixes: d2313084e2 (um: Catch unprotected user memory access)
Signed-off-by: Richard Weinberger <richard@nod.at>
This commit is contained in:
Richard Weinberger 2015-08-09 22:26:33 +02:00
parent 6b1873371c
commit 56b88a3bf9
1 changed files with 1 additions and 1 deletions
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2
arch/um/kernel/trap.c
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@ -220,7 +220,7 @@ unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user,
show_regs(container_of(regs, struct pt_regs, regs));
panic("Segfault with no mm");
}
else if (!is_user && address < TASK_SIZE) {
else if (!is_user && address > PAGE_SIZE && address < TASK_SIZE) {
show_regs(container_of(regs, struct pt_regs, regs));
panic("Kernel tried to access user memory at addr 0x%lx, ip 0x%lx",
address, ip);