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vfio: selftests: Introduce snprintf_assert()

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Introduce snprintf_assert() to protect the users of snprintf() to fail
if the requested operation was truncated due to buffer limits. VFIO
tests and libraries, including a new sysfs library that will be introduced
by an upcoming patch, rely quite heavily on snprintf()s to build PCI
sysfs paths. Having a protection against this will be helpful to prevent
false test failures.

Signed-off-by: Raghavendra Rao Ananta <rananta@google.com>
Reviewed-by: David Matlack <dmatlack@google.com>
Reviewed-by: Vipin Sharma <vipinsh@google.com>
Tested-by: David Matlack <dmatlack@google.com>
Link: https://lore.kernel.org/r/20260505212838.1698034-3-rananta@google.com
Signed-off-by: Alex Williamson <alex@shazbot.org>
This commit is contained in:
Raghavendra Rao Ananta 2026-05-05 21:28:32 +00:00 committed by Alex Williamson
parent ff556bd983
commit 91ee1738a9
4 changed files with 23 additions and 17 deletions
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5
tools/testing/selftests/vfio/lib/include/libvfio/assert.h
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@ -51,4 +51,9 @@
VFIO_ASSERT_EQ(__ret, 0, "ioctl(%s, %s, %s) returned %d\n", #_fd, #_op, #_arg, __ret); \
} while (0)
#define snprintf_assert(_s, _size, _fmt, ...) do { \
int __ret = snprintf(_s, _size, _fmt, ##__VA_ARGS__); \
VFIO_ASSERT_LT(__ret, _size); \
} while (0)
#endif /* SELFTESTS_VFIO_LIB_INCLUDE_LIBVFIO_ASSERT_H */

8
tools/testing/selftests/vfio/lib/vfio_pci_device.c
View File

@ -211,7 +211,7 @@ static unsigned int vfio_pci_get_group_from_dev(const char *bdf)
unsigned int group;
int ret;
snprintf(sysfs_path, PATH_MAX, "%s/%s/iommu_group", PCI_SYSFS_PATH, bdf);
snprintf_assert(sysfs_path, PATH_MAX, "%s/%s/iommu_group", PCI_SYSFS_PATH, bdf);
ret = readlink(sysfs_path, dev_iommu_group_path, sizeof(dev_iommu_group_path));
VFIO_ASSERT_NE(ret, -1, "Failed to get the IOMMU group for device: %s\n", bdf);
@ -231,7 +231,7 @@ static void vfio_pci_group_setup(struct vfio_pci_device *device, const char *bdf
int group;
group = vfio_pci_get_group_from_dev(bdf);
snprintf(group_path, sizeof(group_path), "/dev/vfio/%d", group);
snprintf_assert(group_path, sizeof(group_path), "/dev/vfio/%d", group);
device->group_fd = open(group_path, O_RDWR);
VFIO_ASSERT_GE(device->group_fd, 0, "open(%s) failed\n", group_path);
@ -302,7 +302,7 @@ const char *vfio_pci_get_cdev_path(const char *bdf)
cdev_path = calloc(PATH_MAX, 1);
VFIO_ASSERT_NOT_NULL(cdev_path);
snprintf(dir_path, sizeof(dir_path), "/sys/bus/pci/devices/%s/vfio-dev/", bdf);
snprintf_assert(dir_path, sizeof(dir_path), "/sys/bus/pci/devices/%s/vfio-dev/", bdf);
dir = opendir(dir_path);
VFIO_ASSERT_NOT_NULL(dir, "Failed to open directory %s\n", dir_path);
@ -312,7 +312,7 @@ const char *vfio_pci_get_cdev_path(const char *bdf)
if (strncmp("vfio", entry->d_name, 4))
continue;
snprintf(cdev_path, PATH_MAX, "/dev/vfio/devices/%s", entry->d_name);
snprintf_assert(cdev_path, PATH_MAX, "/dev/vfio/devices/%s", entry->d_name);
break;
}

6
tools/testing/selftests/vfio/vfio_dma_mapping_test.c
View File

@ -44,9 +44,9 @@ static int intel_iommu_mapping_get(const char *bdf, u64 iova,
FILE *file;
char *rest;
snprintf(iommu_mapping_path, sizeof(iommu_mapping_path),
"/sys/kernel/debug/iommu/intel/%s/domain_translation_struct",
bdf);
snprintf_assert(iommu_mapping_path, sizeof(iommu_mapping_path),
"/sys/kernel/debug/iommu/intel/%s/domain_translation_struct",
bdf);
printf("Searching for IOVA 0x%lx in %s\n", iova, iommu_mapping_path);

21
tools/testing/selftests/vfio/vfio_pci_device_test.c
View File

@ -39,16 +39,17 @@ FIXTURE_TEARDOWN(vfio_pci_device_test)
iommu_cleanup(self->iommu);
}
#define read_pci_id_from_sysfs(_file) ({ \
char __sysfs_path[PATH_MAX]; \
char __buf[32]; \
int __fd; \
\
snprintf(__sysfs_path, PATH_MAX, "/sys/bus/pci/devices/%s/%s", device_bdf, _file); \
ASSERT_GT((__fd = open(__sysfs_path, O_RDONLY)), 0); \
ASSERT_GT(read(__fd, __buf, ARRAY_SIZE(__buf)), 0); \
ASSERT_EQ(0, close(__fd)); \
(u16)strtoul(__buf, NULL, 0); \
#define read_pci_id_from_sysfs(_file) ({ \
char __sysfs_path[PATH_MAX]; \
char __buf[32]; \
int __fd; \
\
snprintf_assert(__sysfs_path, PATH_MAX, "/sys/bus/pci/devices/%s/%s", \
device_bdf, _file); \
ASSERT_GT((__fd = open(__sysfs_path, O_RDONLY)), 0); \
ASSERT_GT(read(__fd, __buf, ARRAY_SIZE(__buf)), 0); \
ASSERT_EQ(0, close(__fd)); \
(u16)strtoul(__buf, NULL, 0); \
})
TEST_F(vfio_pci_device_test, config_space_read_write)