In preparation for removing the strlcat() API[1], replace its uses in orangefs_prepare_debugfs_help_string().
The function accumulates a variable number of keyword lines into a fixed buffer, which is what seq_buf is for. Each keyword line becomes a single seq_buf_printf(). The old code detected overflow through the return value of the last strlcat(). The seq_buf_has_overflowed() function reports the same condition directly. The final transfer into debug_help_string lands in a buffer that was just zeroed, so it is a plain copy and becomes strscpy(). The output is unchanged in all cases. Link: https://github.com/KSPP/linux/issues/370 [1] Signed-off-by: Ian Bridges <[email protected]> --- The patch was tested as follows: - An x86_64 build of fs/orangefs/orangefs-debugfs.o at W=1 produces no warnings. - A userspace comparison of the old and new construction ran with randomized keyword lists and buffer sizes. The buffer bytes, the overflow decisions, and the final copies were identical in every case. - Base and patched orangefs.ko were loaded in a QEMU guest. The complete /sys/kernel/debug/orangefs/debug-help file is identical before and after the change. fs/orangefs/orangefs-debugfs.c | 38 ++++++++++++++-------------------- 1 file changed, 15 insertions(+), 23 deletions(-) diff --git a/fs/orangefs/orangefs-debugfs.c b/fs/orangefs/orangefs-debugfs.c index 69bd73a2b556..107942ce1adf 100644 --- a/fs/orangefs/orangefs-debugfs.c +++ b/fs/orangefs/orangefs-debugfs.c @@ -36,6 +36,7 @@ * no need for a "verbose". */ #include <linux/debugfs.h> +#include <linux/seq_buf.h> #include <linux/slab.h> #include <linux/uaccess.h> @@ -622,7 +623,7 @@ int orangefs_prepare_debugfs_help_string(int at_boot) char *client_title = "Client Debug Keywords:\n"; char *kernel_title = "Kernel Debug Keywords:\n"; size_t string_size = DEBUG_HELP_STRING_SIZE; - size_t result_size; + struct seq_buf sb; size_t i; char *new; int rc = -EINVAL; @@ -640,16 +641,13 @@ int orangefs_prepare_debugfs_help_string(int at_boot) } /* - * strlcat(dst, src, size) will append at most - * "size - strlen(dst) - 1" bytes of src onto dst, - * null terminating the result, and return the total - * length of the string it tried to create. - * * We'll just plow through here building our new debug - * help string and let strlcat take care of assuring that - * dst doesn't overflow. + * help string in a seq_buf, which is bounded by the buffer + * size, keeps the string terminated, and records whether + * anything failed to fit. */ - strlcat(new, client_title, string_size); + seq_buf_init(&sb, new, string_size); + seq_buf_printf(&sb, "%s", client_title); if (!at_boot) { @@ -664,24 +662,18 @@ int orangefs_prepare_debugfs_help_string(int at_boot) goto out; } - for (i = 0; i < cdm_element_count; i++) { - strlcat(new, "\t", string_size); - strlcat(new, cdm_array[i].keyword, string_size); - strlcat(new, "\n", string_size); - } + for (i = 0; i < cdm_element_count; i++) + seq_buf_printf(&sb, "\t%s\n", cdm_array[i].keyword); } - strlcat(new, "\n", string_size); - strlcat(new, kernel_title, string_size); + seq_buf_printf(&sb, "\n%s", kernel_title); - for (i = 0; i < num_kmod_keyword_mask_map; i++) { - strlcat(new, "\t", string_size); - strlcat(new, s_kmod_keyword_mask_map[i].keyword, string_size); - result_size = strlcat(new, "\n", string_size); - } + for (i = 0; i < num_kmod_keyword_mask_map; i++) + seq_buf_printf(&sb, "\t%s\n", + s_kmod_keyword_mask_map[i].keyword); /* See if we tried to put too many bytes into "new"... */ - if (result_size >= string_size) { + if (seq_buf_has_overflowed(&sb)) { kfree(new); goto out; } @@ -691,7 +683,7 @@ int orangefs_prepare_debugfs_help_string(int at_boot) } else { mutex_lock(&orangefs_help_file_lock); memset(debug_help_string, 0, DEBUG_HELP_STRING_SIZE); - strlcat(debug_help_string, new, string_size); + strscpy(debug_help_string, new, string_size); mutex_unlock(&orangefs_help_file_lock); kfree(new); } -- 2.47.3
