[ Upstream commit ffbf4fb9b5c12ff878a10ea17997147ea4ebea6f ]
When CONFIG_DEBUG_BUGVERBOSE=n, we fail to add necessary padding bytes
to bug_table entries, and as a result the last entry in a bug table will
be ignored, potentially leading to an unexpected panic(). All prior
entries in the table will be handled correctly.
The arm64 ABI requires that struct fields of up to 8 bytes are
naturally-aligned, with padding added within a struct such that struct
are suitably aligned within arrays.
When CONFIG_DEBUG_BUGVERPOSE=y, the layout of a bug_entry is:
struct bug_entry {
signed int bug_addr_disp; // 4 bytes
signed int file_disp; // 4 bytes
unsigned short line; // 2 bytes
unsigned short flags; // 2 bytes
}
... with 12 bytes total, requiring 4-byte alignment.
When CONFIG_DEBUG_BUGVERBOSE=n, the layout of a bug_entry is:
struct bug_entry {
signed int bug_addr_disp; // 4 bytes
unsigned short flags; // 2 bytes
< implicit padding > // 2 bytes
}
... with 8 bytes total, with 6 bytes of data and 2 bytes of trailing
padding, requiring 4-byte alginment.
When we create a bug_entry in assembly, we align the start of the entry
to 4 bytes, which implicitly handles padding for any prior entries.
However, we do not align the end of the entry, and so when
CONFIG_DEBUG_BUGVERBOSE=n, the final entry lacks the trailing padding
bytes.
For the main kernel image this is not a problem as find_bug() doesn't
depend on the trailing padding bytes when searching for entries:
for (bug = __start___bug_table; bug < __stop___bug_table; ++bug)
if (bugaddr == bug_addr(bug))
return bug;
However for modules, module_bug_finalize() depends on the trailing
bytes when calculating the number of entries:
mod->num_bugs = sechdrs[i].sh_size / sizeof(struct bug_entry);
... and as the last bug_entry lacks the necessary padding bytes, this entry
will not be counted, e.g. in the case of a single entry:
sechdrs[i].sh_size == 6
sizeof(struct bug_entry) == 8;
sechdrs[i].sh_size / sizeof(struct bug_entry) == 0;
Consequently module_find_bug() will miss the last bug_entry when it does:
for (i = 0; i < mod->num_bugs; ++i, ++bug)
if (bugaddr == bug_addr(bug))
goto out;
... which can lead to a kenrel panic due to an unhandled bug.
This can be demonstrated with the following module:
static int __init buginit(void)
{
WARN(1, "hello\n");
return 0;
}
static void __exit bugexit(void)
{
}
module_init(buginit);
module_exit(bugexit);
MODULE_LICENSE("GPL");
... which will trigger a kernel panic when loaded:
------------[ cut here ]------------
hello
Unexpected kernel BRK exception at EL1
Internal error: BRK handler: 00000000f2000800 [#1] PREEMPT SMP
Modules linked in: hello(O+)
CPU: 0 PID: 50 Comm: insmod Tainted: G O 6.9.1 #8
Hardware name: linux,dummy-virt (DT)
pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : buginit+0x18/0x1000 [hello]
lr : buginit+0x18/0x1000 [hello]
sp : ffff800080533ae0
x29: ffff800080533ae0 x28: 0000000000000000 x27: 0000000000000000
x26: ffffaba8c4e70510 x25: ffff800080533c30 x24: ffffaba8c4a28a58
x23: 0000000000000000 x22: 0000000000000000 x21: ffff3947c0eab3c0
x20: ffffaba8c4e3f000 x19: ffffaba846464000 x18: 0000000000000006
x17: 0000000000000000 x16: ffffaba8c2492834 x15: 0720072007200720
x14: 0720072007200720 x13: ffffaba8c49b27c8 x12: 0000000000000312
x11: 0000000000000106 x10: ffffaba8c4a0a7c8 x9 : ffffaba8c49b27c8
x8 : 00000000ffffefff x7 : ffffaba8c4a0a7c8 x6 : 80000000fffff000
x5 : 0000000000000107 x4 : 0000000000000000 x3 : 0000000000000000
x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff3947c0eab3c0
Call trace:
buginit+0x18/0x1000 [hello]
do_one_initcall+0x80/0x1c8
do_init_module+0x60/0x218
load_module+0x1ba4/0x1d70
__do_sys_init_module+0x198/0x1d0
__arm64_sys_init_module+0x1c/0x28
invoke_syscall+0x48/0x114
el0_svc_common.constprop.0+0x40/0xe0
do_el0_svc+0x1c/0x28
el0_svc+0x34/0xd8
el0t_64_sync_handler+0x120/0x12c
el0t_64_sync+0x190/0x194
Code: d0ffffe0 910003fd 91000000 9400000b (d4210000)
---[ end trace 0000000000000000 ]---
Kernel panic - not syncing: BRK handler: Fatal exception
Fix this by always aligning the end of a bug_entry to 4 bytes, which is
correct regardless of CONFIG_DEBUG_BUGVERBOSE.
Fixes: 9fb7410f955f ("arm64/BUG: Use BRK instruction for generic BUG traps")
Signed-off-by: Yuanbin Xie <xieyuanbin1@huawei.com>
Signed-off-by: Jiangfeng Xiao <xiaojiangfeng@huawei.com>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/1716212077-43826-1-git-send-email-xiaojiangfeng@huawei.com
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
commit 3c0696076aad60a2f04c019761921954579e1b0e upstream.
It is currently possible for a userspace application to enter an
infinite page fault loop when using HugeTLB pages implemented with
contiguous PTEs when HAFDBS is not available. This happens because:
1. The kernel may sometimes write PTEs that are sw-dirty but hw-clean
(PTE_DIRTY | PTE_RDONLY | PTE_WRITE).
2. If, during a write, the CPU uses a sw-dirty, hw-clean PTE in handling
the memory access on a system without HAFDBS, we will get a page
fault.
3. HugeTLB will check if it needs to update the dirty bits on the PTE.
For contiguous PTEs, it will check to see if the pgprot bits need
updating. In this case, HugeTLB wants to write a sequence of
sw-dirty, hw-dirty PTEs, but it finds that all the PTEs it is about
to overwrite are all pte_dirty() (pte_sw_dirty() => pte_dirty()),
so it thinks no update is necessary.
We can get the kernel to write a sw-dirty, hw-clean PTE with the
following steps (showing the relevant VMA flags and pgprot bits):
i. Create a valid, writable contiguous PTE.
VMA vmflags: VM_SHARED | VM_READ | VM_WRITE
VMA pgprot bits: PTE_RDONLY | PTE_WRITE
PTE pgprot bits: PTE_DIRTY | PTE_WRITE
ii. mprotect the VMA to PROT_NONE.
VMA vmflags: VM_SHARED
VMA pgprot bits: PTE_RDONLY
PTE pgprot bits: PTE_DIRTY | PTE_RDONLY
iii. mprotect the VMA back to PROT_READ | PROT_WRITE.
VMA vmflags: VM_SHARED | VM_READ | VM_WRITE
VMA pgprot bits: PTE_RDONLY | PTE_WRITE
PTE pgprot bits: PTE_DIRTY | PTE_WRITE | PTE_RDONLY
Make it impossible to create a writeable sw-dirty, hw-clean PTE with
pte_modify(). Such a PTE should be impossible to create, and there may
be places that assume that pte_dirty() implies pte_hw_dirty().
Signed-off-by: James Houghton <jthoughton@google.com>
Fixes: 031e6e6b4e12 ("arm64: hugetlb: Avoid unnecessary clearing in huge_ptep_set_access_flags")
Cc: <stable@vger.kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Link: https://lore.kernel.org/r/20231204172646.2541916-3-jthoughton@google.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Since we are compiling for a single chipset that is known to support LSE,
the system_uses_lse_atomics() static branch can be eliminated entirely.
Therefore, make system_uses_lse_atomics() always true to always use LSE
atomics, and update ARM64_LSE_ATOMIC_INSN() users to get rid of the extra
nops used for alternatives patching at runtime.
This reduces generated code size by removing LL/SC atomics, which improves
instruction cache footprint.
Signed-off-by: Sultan Alsawaf <sultan@kerneltoast.com>
commit b3a0c010e900a9f89dcd99f10bd8f7538d21b0a9 upstream.
Currently do_sysinstr() and do_cp15instr() are marked with
NOKPROBE_SYMBOL(). However, these are only called for exceptions taken
from EL0, and there is no risk of recursion in kprobes, so this is not
necessary.
Remove the NOKPROBE_SYMBOL() annotation, and rename the two functions to
more clearly indicate that these are solely for exceptions taken from
EL0, better matching the names used by the lower level entry points in
entry-common.c.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Joey Gouly <joey.gouly@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20221019144123.612388-2-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 18906ff9af6517c20763ed63dab602a4150794f7 upstream.
Recently, we reworked a lot of code to consistentlt pass ESR_ELx as a
64-bit quantity. However, we missed that this can be passed into die()
and __die() as the 'err' parameter where it is truncated to a 32-bit
int.
As notify_die() already takes 'err' as a long, this patch changes die()
and __die() to also take 'err' as a long, ensuring that the full value
of ESR_ELx is retained.
At the same time, die() is updated to consistently log 'err' as a
zero-padded 64-bit quantity.
Subsequent patches will pass the ESR_ELx value to die() for a number of
exceptions.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Alexandru Elisei <alexandru.elisei@arm.com>
Cc: Amit Daniel Kachhap <amit.kachhap@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20220913101732.3925290-3-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
