| Message ID | 20250415203354.4109415-1-smostafa@google.com (mailing list archive) |
|---|---|
| State | In Next |
| Commit | 9b044614be12d78d3a93767708b8d02fb7dfa9b0 |
| Headers | show |
| Series | [v2] lib/test_ubsan.c: Fix panic from test_ubsan_out_of_bounds | expand |
On Tue, Apr 15, 2025 at 08:33:54PM +0000, Mostafa Saleh wrote: > Running lib_ubsan.ko on arm64 (without CONFIG_UBSAN_TRAP) panics the > kernel > > [ 31.616546] Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: test_ubsan_out_of_bounds+0x158/0x158 [test_ubsan] > [ 31.646817] CPU: 3 UID: 0 PID: 179 Comm: insmod Not tainted 6.15.0-rc2 #1 PREEMPT > [ 31.648153] Hardware name: linux,dummy-virt (DT) > [ 31.648970] Call trace: > [ 31.649345] show_stack+0x18/0x24 (C) > [ 31.650960] dump_stack_lvl+0x40/0x84 > [ 31.651559] dump_stack+0x18/0x24 > [ 31.652264] panic+0x138/0x3b4 > [ 31.652812] __ktime_get_real_seconds+0x0/0x10 > [ 31.653540] test_ubsan_load_invalid_value+0x0/0xa8 [test_ubsan] > [ 31.654388] init_module+0x24/0xff4 [test_ubsan] > [ 31.655077] do_one_initcall+0xd4/0x280 > [ 31.655680] do_init_module+0x58/0x2b4 > > That happens because the test corrupts other data in the stack: > 400: d5384108 mrs x8, sp_el0 > 404: f9426d08 ldr x8, [x8, #1240] > 408: f85f83a9 ldur x9, [x29, #-8] > 40c: eb09011f cmp x8, x9 > 410: 54000301 b.ne 470 <test_ubsan_out_of_bounds+0x154> // b.any > > As there is no guarantee the compiler will order the local variables > as declared in the module: > volatile char above[4] = { }; /* Protect surrounding memory. */ > volatile int arr[4]; > volatile char below[4] = { }; /* Protect surrounding memory. */ > > There is another problem where the out-of-bound index is 5 which is larger > than the extra surrounding memory for protection. > > So, use a struct to enforce the ordering, and fix the index to be 4. > Also, remove some of the volatiles and rely on OPTIMIZER_HIDE_VAR() > > Signed-off-by: Mostafa Saleh <smostafa@google.com> Looks good; thanks! Reviewed-by: Kees Cook <kees@kernel.org>
On Tue, 15 Apr 2025 20:33:54 +0000, Mostafa Saleh wrote: > Running lib_ubsan.ko on arm64 (without CONFIG_UBSAN_TRAP) panics the > kernel > > [ 31.616546] Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: test_ubsan_out_of_bounds+0x158/0x158 [test_ubsan] > [ 31.646817] CPU: 3 UID: 0 PID: 179 Comm: insmod Not tainted 6.15.0-rc2 #1 PREEMPT > [ 31.648153] Hardware name: linux,dummy-virt (DT) > [ 31.648970] Call trace: > [ 31.649345] show_stack+0x18/0x24 (C) > [ 31.650960] dump_stack_lvl+0x40/0x84 > [ 31.651559] dump_stack+0x18/0x24 > [ 31.652264] panic+0x138/0x3b4 > [ 31.652812] __ktime_get_real_seconds+0x0/0x10 > [ 31.653540] test_ubsan_load_invalid_value+0x0/0xa8 [test_ubsan] > [ 31.654388] init_module+0x24/0xff4 [test_ubsan] > [ 31.655077] do_one_initcall+0xd4/0x280 > [ 31.655680] do_init_module+0x58/0x2b4 > > [...] Applied to for-linus/hardening, thanks! [1/1] lib/test_ubsan.c: Fix panic from test_ubsan_out_of_bounds https://git.kernel.org/kees/c/7fd007c84e4b Take care,
diff --git a/lib/test_ubsan.c b/lib/test_ubsan.c index 8772e5edaa4f..a4b6f52b9c57 100644 --- a/lib/test_ubsan.c +++ b/lib/test_ubsan.c @@ -77,18 +77,22 @@ static void test_ubsan_shift_out_of_bounds(void) static void test_ubsan_out_of_bounds(void) { - volatile int i = 4, j = 5, k = -1; - volatile char above[4] = { }; /* Protect surrounding memory. */ - volatile int arr[4]; - volatile char below[4] = { }; /* Protect surrounding memory. */ + int i = 4, j = 4, k = -1; + volatile struct { + char above[4]; /* Protect surrounding memory. */ + int arr[4]; + char below[4]; /* Protect surrounding memory. */ + } data; - above[0] = below[0]; + OPTIMIZER_HIDE_VAR(i); + OPTIMIZER_HIDE_VAR(j); + OPTIMIZER_HIDE_VAR(k); UBSAN_TEST(CONFIG_UBSAN_BOUNDS, "above"); - arr[j] = i; + data.arr[j] = i; UBSAN_TEST(CONFIG_UBSAN_BOUNDS, "below"); - arr[k] = i; + data.arr[k] = i; } enum ubsan_test_enum {
Running lib_ubsan.ko on arm64 (without CONFIG_UBSAN_TRAP) panics the kernel [ 31.616546] Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: test_ubsan_out_of_bounds+0x158/0x158 [test_ubsan] [ 31.646817] CPU: 3 UID: 0 PID: 179 Comm: insmod Not tainted 6.15.0-rc2 #1 PREEMPT [ 31.648153] Hardware name: linux,dummy-virt (DT) [ 31.648970] Call trace: [ 31.649345] show_stack+0x18/0x24 (C) [ 31.650960] dump_stack_lvl+0x40/0x84 [ 31.651559] dump_stack+0x18/0x24 [ 31.652264] panic+0x138/0x3b4 [ 31.652812] __ktime_get_real_seconds+0x0/0x10 [ 31.653540] test_ubsan_load_invalid_value+0x0/0xa8 [test_ubsan] [ 31.654388] init_module+0x24/0xff4 [test_ubsan] [ 31.655077] do_one_initcall+0xd4/0x280 [ 31.655680] do_init_module+0x58/0x2b4 That happens because the test corrupts other data in the stack: 400: d5384108 mrs x8, sp_el0 404: f9426d08 ldr x8, [x8, #1240] 408: f85f83a9 ldur x9, [x29, #-8] 40c: eb09011f cmp x8, x9 410: 54000301 b.ne 470 <test_ubsan_out_of_bounds+0x154> // b.any As there is no guarantee the compiler will order the local variables as declared in the module: volatile char above[4] = { }; /* Protect surrounding memory. */ volatile int arr[4]; volatile char below[4] = { }; /* Protect surrounding memory. */ There is another problem where the out-of-bound index is 5 which is larger than the extra surrounding memory for protection. So, use a struct to enforce the ordering, and fix the index to be 4. Also, remove some of the volatiles and rely on OPTIMIZER_HIDE_VAR() Signed-off-by: Mostafa Saleh <smostafa@google.com> --- v2: - Use struct instead of reading. - remove some of the volatiles. --- lib/test_ubsan.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-)