On Thu, 14 Nov 2024 19:01:41 +0800 Li Huafei lihuafei1@huawei.com wrote:
During fuzz testing, the following warning was discovered:
different return values (15 and 11) from vsnprintf("%*pbl ", ...)
test:keyward is WARNING in kvasprintf WARNING: CPU: 55 PID: 1168477 at lib/kasprintf.c:30 kvasprintf+0x121/0x130 Call Trace: kvasprintf+0x121/0x130 kasprintf+0xa6/0xe0 bitmap_print_to_buf+0x89/0x100 core_siblings_list_read+0x7e/0xb0 kernfs_file_read_iter+0x15b/0x270 new_sync_read+0x153/0x260 vfs_read+0x215/0x290 ksys_read+0xb9/0x160 do_syscall_64+0x56/0x100 entry_SYSCALL_64_after_hwframe+0x78/0xe2
The call trace shows that kvasprintf() reported this warning during the printing of core_siblings_list. kvasprintf() has several steps:
(1) First, calculate the length of the resulting formatted string.
(2) Allocate a buffer based on the returned length.
(3) Then, perform the actual string formatting.
(4) Check whether the lengths of the formatted strings returned in steps (1) and (2) are consistent.
If the core_cpumask is modified between steps (1) and (3), the lengths obtained in these two steps may not match. Indeed our test includes cpu hotplugging, which should modify core_cpumask while printing.
To fix this issue, cache the cpumask into a temporary variable before calling cpumap_print_{list, cpumask}_to_buf(), to keep it unchanged during the printing process.
Fixes: bb9ec13d156e ("topology: use bin_attribute to break the size limitation of cpumap ABI") Cc: stable@vger.kernel.org Signed-off-by: Li Huafei lihuafei1@huawei.com
Makes sense. Trivial comment inline.
Reviewed-by: Jonathan Cameron Jonathan.Cameron@huawei.com
Changes in v2:
- Return an error when calling alloc_cpumask_var() fails instead of returning a size of 0.
- Add Cc (to stable) tag.
drivers/base/topology.c | 24 ++++++++++++++++++++---- 1 file changed, 20 insertions(+), 4 deletions(-)
diff --git a/drivers/base/topology.c b/drivers/base/topology.c index 89f98be5c5b9..d293cbd253e4 100644 --- a/drivers/base/topology.c +++ b/drivers/base/topology.c @@ -27,9 +27,17 @@ static ssize_t name##_read(struct file *file, struct kobject *kobj, \ loff_t off, size_t count) \ { \ struct device *dev = kobj_to_dev(kobj); \
- cpumask_var_t mask; \
- ssize_t n; \ \
- return cpumap_print_bitmask_to_buf(buf, topology_##mask(dev->id), \
off, count); \
- if (!alloc_cpumask_var(&mask, GFP_KERNEL)) \
return -ENOMEM; \
Good catch. Could use __free(free_cpumask_var) but that is a bit messy given it's not a conventional allocation that returns a pointer. So probably not worth doing just to save a single manual free call.
\- cpumask_copy(mask, topology_##mask(dev->id)); \
- n = cpumap_print_bitmask_to_buf(buf, mask, off, count); \
- free_cpumask_var(mask); \
\- return n; \
} \ \ static ssize_t name##_list_read(struct file *file, struct kobject *kobj, \ @@ -37,9 +45,17 @@ static ssize_t name##_list_read(struct file *file, struct kobject *kobj, \ loff_t off, size_t count) \ { \ struct device *dev = kobj_to_dev(kobj); \
- cpumask_var_t mask; \
- ssize_t n; \
\- if (!alloc_cpumask_var(&mask, GFP_KERNEL)) \
return -ENOMEM; \\- cpumask_copy(mask, topology_##mask(dev->id)); \
- n = cpumap_print_list_to_buf(buf, mask, off, count); \
- free_cpumask_var(mask); \ \
- return cpumap_print_list_to_buf(buf, topology_##mask(dev->id), \
off, count); \
- return n; \
} define_id_show_func(physical_package_id, "%d");