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tracing/user_events: Fix non-spaced field matching
[ Upstream commitbd125a0840
] When the ABI was updated to prevent same name w/different args, it missed an important corner case when fields don't end with a space. Typically, space is used for fields to help separate them, like "u8 field1; u8 field2". If no spaces are used, like "u8 field1;u8 field2", then the parsing works for the first time. However, the match check fails on a subsequent register, leading to confusion. This is because the match check uses argv_split() and assumes that all fields will be split upon the space. When spaces are used, we get back { "u8", "field1;" }, without spaces we get back { "u8", "field1;u8" }. This causes a mismatch, and the user program gets back -EADDRINUSE. Add a method to detect this case before calling argv_split(). If found force a space after the field separator character ';'. This ensures all cases work properly for matching. With this fix, the following are all treated as matching: u8 field1;u8 field2 u8 field1; u8 field2 u8 field1;\tu8 field2 u8 field1;\nu8 field2 Link: https://lore.kernel.org/linux-trace-kernel/20240423162338.292-2-beaub@linux.microsoft.com Fixes:ba470eebc2
("tracing/user_events: Prevent same name but different args event") Signed-off-by: Beau Belgrave <beaub@linux.microsoft.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
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@ -1923,6 +1923,80 @@ static int user_event_trace_register(struct user_event *user)
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return ret;
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return ret;
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}
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}
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/*
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* Counts how many ';' without a trailing space are in the args.
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*/
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static int count_semis_no_space(char *args)
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{
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int count = 0;
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while ((args = strchr(args, ';'))) {
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args++;
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if (!isspace(*args))
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count++;
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}
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return count;
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}
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/*
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* Copies the arguments while ensuring all ';' have a trailing space.
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*/
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static char *insert_space_after_semis(char *args, int count)
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{
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char *fixed, *pos;
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int len;
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len = strlen(args) + count;
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fixed = kmalloc(len + 1, GFP_KERNEL);
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if (!fixed)
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return NULL;
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pos = fixed;
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/* Insert a space after ';' if there is no trailing space. */
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while (*args) {
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*pos = *args++;
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if (*pos++ == ';' && !isspace(*args))
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*pos++ = ' ';
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}
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*pos = '\0';
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return fixed;
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}
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static char **user_event_argv_split(char *args, int *argc)
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{
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char **split;
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char *fixed;
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int count;
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/* Count how many ';' without a trailing space */
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count = count_semis_no_space(args);
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/* No fixup is required */
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if (!count)
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return argv_split(GFP_KERNEL, args, argc);
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/* We must fixup 'field;field' to 'field; field' */
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fixed = insert_space_after_semis(args, count);
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if (!fixed)
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return NULL;
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/* We do a normal split afterwards */
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split = argv_split(GFP_KERNEL, fixed, argc);
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/* We can free since argv_split makes a copy */
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kfree(fixed);
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return split;
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}
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/*
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/*
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* Parses the event name, arguments and flags then registers if successful.
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* Parses the event name, arguments and flags then registers if successful.
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* The name buffer lifetime is owned by this method for success cases only.
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* The name buffer lifetime is owned by this method for success cases only.
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@ -1946,7 +2020,7 @@ static int user_event_parse(struct user_event_group *group, char *name,
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return -EPERM;
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return -EPERM;
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if (args) {
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if (args) {
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argv = argv_split(GFP_KERNEL, args, &argc);
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argv = user_event_argv_split(args, &argc);
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if (!argv)
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if (!argv)
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return -ENOMEM;
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return -ENOMEM;
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