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author | Anshuman Khandual <anshuman.khandual@arm.com> | 2019-06-03 12:11:22 +0530 |
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committer | Catalin Marinas <catalin.marinas@arm.com> | 2019-06-04 15:26:18 +0100 |
commit | a0509313d5dea0a27a5968f04bd556d05e6349fd (patch) | |
tree | b16a91ca2728bf09ac0d42f6b2a0e75b5f771aa3 /arch/arm64/mm | |
parent | 01de1776f62e6437ccd207181ec503e8a56e6128 (diff) | |
download | linux-a0509313d5dea0a27a5968f04bd556d05e6349fd.tar.bz2 |
arm64/mm: Drop mmap_sem before calling __do_kernel_fault()
There is an inconsistency between down_read_trylock() success and failure
paths while dealing with kernel access for non exception table areas where
it calls __do_kernel_fault(). In case of failure it just bails out without
holding mmap_sem but when it succeeds it does so while holding mmap_sem.
Fix this inconsistency by just dropping mmap_sem in success path as well.
__do_kernel_fault() calls die_kernel_fault() which then calls show_pte().
show_pte() in this path might become bit more unreliable without holding
mmap_sem. But there are already instances [1] in do_page_fault() where
die_kernel_fault() gets called without holding mmap_sem. show_pte() can
be made more robust independently but in a later patch.
[1] Conditional block for (is_ttbr0_addr && is_el1_permission_fault)
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64/mm')
-rw-r--r-- | arch/arm64/mm/fault.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index 392386a693fe..2256a1a09f1b 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -504,8 +504,10 @@ retry: */ might_sleep(); #ifdef CONFIG_DEBUG_VM - if (!user_mode(regs) && !search_exception_tables(regs->pc)) + if (!user_mode(regs) && !search_exception_tables(regs->pc)) { + up_read(&mm->mmap_sem); goto no_context; + } #endif } |