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| author | Evgenii Stepanov <eugenis@google.com> | 2022-01-25 21:22:17 +0300 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2022-01-26 21:58:12 +0300 |
| commit | 3758a6c74e08bdc15ccccd6872a6ad37d165239a (patch) | |
| tree | 5080cd205c46c2dbf2f9293b91726d2fe30234df /arch/arm64 | |
| parent | 1e0924bd09916fab795fc2a21ec1d148f24299fd (diff) | |
| download | linux-3758a6c74e08bdc15ccccd6872a6ad37d165239a.tar.xz | |
arm64: extable: fix load_unaligned_zeropad() reg indices
In ex_handler_load_unaligned_zeropad() we erroneously extract the data and
addr register indices from ex->type rather than ex->data. As ex->type will
contain EX_TYPE_LOAD_UNALIGNED_ZEROPAD (i.e. 4):
* We'll always treat X0 as the address register, since EX_DATA_REG_ADDR is
extracted from bits [9:5]. Thus, we may attempt to dereference an
arbitrary address as X0 may hold an arbitrary value.
* We'll always treat X4 as the data register, since EX_DATA_REG_DATA is
extracted from bits [4:0]. Thus we will corrupt X4 and cause arbitrary
behaviour within load_unaligned_zeropad() and its caller.
Fix this by extracting both values from ex->data as originally intended.
On an MTE-enabled QEMU image we are hitting the following crash:
Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
Call trace:
fixup_exception+0xc4/0x108
__do_kernel_fault+0x3c/0x268
do_tag_check_fault+0x3c/0x104
do_mem_abort+0x44/0xf4
el1_abort+0x40/0x64
el1h_64_sync_handler+0x60/0xa0
el1h_64_sync+0x7c/0x80
link_path_walk+0x150/0x344
path_openat+0xa0/0x7dc
do_filp_open+0xb8/0x168
do_sys_openat2+0x88/0x17c
__arm64_sys_openat+0x74/0xa0
invoke_syscall+0x48/0x148
el0_svc_common+0xb8/0xf8
do_el0_svc+0x28/0x88
el0_svc+0x24/0x84
el0t_64_sync_handler+0x88/0xec
el0t_64_sync+0x1b4/0x1b8
Code: f8695a69 71007d1f 540000e0 927df12a (f940014a)
Fixes: 753b32368705 ("arm64: extable: add load_unaligned_zeropad() handler")
Cc: <stable@vger.kernel.org> # 5.16.x
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Evgenii Stepanov <eugenis@google.com>
Link: https://lore.kernel.org/r/20220125182217.2605202-1-eugenis@google.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64')
| -rw-r--r-- | arch/arm64/mm/extable.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/arm64/mm/extable.c b/arch/arm64/mm/extable.c index c0181e60cc98..489455309695 100644 --- a/arch/arm64/mm/extable.c +++ b/arch/arm64/mm/extable.c @@ -40,8 +40,8 @@ static bool ex_handler_load_unaligned_zeropad(const struct exception_table_entry *ex, struct pt_regs *regs) { - int reg_data = FIELD_GET(EX_DATA_REG_DATA, ex->type); - int reg_addr = FIELD_GET(EX_DATA_REG_ADDR, ex->type); + int reg_data = FIELD_GET(EX_DATA_REG_DATA, ex->data); + int reg_addr = FIELD_GET(EX_DATA_REG_ADDR, ex->data); unsigned long data, addr, offset; addr = pt_regs_read_reg(regs, reg_addr); |