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usb: gadget: f_uac2: Replace snprintf() with the safer scnprintf() variant

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There is a general misunderstanding amongst engineers that {v}snprintf()
returns the length of the data *actually* encoded into the destination
array.  However, as per the C99 standard {v}snprintf() really returns
the length of the data that *would have been* written if there were
enough space for it.  This misunderstanding has led to buffer-overruns
in the past.  It's generally considered safer to use the {v}scnprintf()
variants in their place (or even sprintf() in simple cases).  So let's
do that.

Link: https://lwn.net/Articles/69419/
Link: https://github.com/KSPP/linux/issues/105
Cc: James Gruber <jimmyjgruber@gmail.com>
Cc: Yadwinder Singh <yadi.brar01@gmail.com>
Cc: Jaswinder Singh <jaswinder.singh@linaro.org>
Cc: Ruslan Bilovol <ruslan.bilovol@gmail.com>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20231213164246.1021885-4-lee@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Lee Jones 2023-12-13 16:42:32 +00:00 committed by Greg Kroah-Hartman
parent c1a371866d
commit 60034e0aed
1 changed files with 3 additions and 3 deletions
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6
drivers/usb/gadget/function/f_uac2.c
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@ -2045,7 +2045,7 @@ static ssize_t f_uac2_opts_##name##_show(struct config_item *item, \
int result; \
\
mutex_lock(&opts->lock); \
result = snprintf(page, sizeof(opts->name), "%s", opts->name); \
result = scnprintf(page, sizeof(opts->name), "%s", opts->name); \
mutex_unlock(&opts->lock); \
\
return result; \
@ -2063,7 +2063,7 @@ static ssize_t f_uac2_opts_##name##_store(struct config_item *item, \
goto end; \
} \
\
ret = snprintf(opts->name, min(sizeof(opts->name), len), \
ret = scnprintf(opts->name, min(sizeof(opts->name), len), \
"%s", page); \
\
end: \
@ -2187,7 +2187,7 @@ static struct usb_function_instance *afunc_alloc_inst(void)
opts->req_number = UAC2_DEF_REQ_NUM;
opts->fb_max = FBACK_FAST_MAX;
snprintf(opts->function_name, sizeof(opts->function_name), "Source/Sink");
scnprintf(opts->function_name, sizeof(opts->function_name), "Source/Sink");
opts->p_terminal_type = UAC2_DEF_P_TERM_TYPE;
opts->c_terminal_type = UAC2_DEF_C_TERM_TYPE;