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authorEvgenii Stepanov <eugenis@google.com>2022-01-25 19:22:17 +0100
committerCatalin Marinas <catalin.marinas@arm.com>2022-01-26 19:58:12 +0100
commit3758a6c74e08bdc15ccccd6872a6ad37d165239a (patch)
tree5080cd205c46c2dbf2f9293b91726d2fe30234df
parentarm64: Mark start_backtrace() notrace and NOKPROBE_SYMBOL (diff)
downloadlinux-3758a6c74e08bdc15ccccd6872a6ad37d165239a.tar.xz
linux-3758a6c74e08bdc15ccccd6872a6ad37d165239a.zip
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>
-rw-r--r--arch/arm64/mm/extable.c4
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);