On Fri, Apr 2, 2021 at 8:17 PM Nick Desaulniers <ndesaulni...@google.com> wrote: > > Thanks for the patch! > > + akpm (please remember to run ./scripts/get_maintainer.pl on your patch > files) > > On Fri, Apr 2, 2021 at 2:41 AM Gioh Kim <gi-oh....@ionos.com> wrote: > > > > As the name shows, it checks if strings are equal in case insensitive > > manner. I found some cases using strncasecmp to check the entire > > strings and they would not work as intended. > > > > For example, drivers/infiniband/ulp/rtrs/rtrs-clt-sysfs.c uses > > strncasecmp to check that the input via sysfs is "mi". But it would > > work even-if the input is "min-wrongcommand". > > And also drivers/pnp/interface.c checks "disable" command with > > strncasecmp but it would also work if the command is "disable-wrong". > > Perhaps those callers should be using strcasecmp then, rather than > strncasecmp? > > Also, if they're being liberal in accepting either case, I don't see > why the sysfs nodes should be strict in rejecting trailing input at > that point. >
On Fri, Apr 2, 2021 at 8:17 PM Nick Desaulniers <ndesaulni...@google.com> wrote: > > Thanks for the patch! > > + akpm (please remember to run ./scripts/get_maintainer.pl on your patch > files) > > On Fri, Apr 2, 2021 at 2:41 AM Gioh Kim <gi-oh....@ionos.com> wrote: > > > > As the name shows, it checks if strings are equal in case insensitive > > manner. I found some cases using strncasecmp to check the entire > > strings and they would not work as intended. > > > > For example, drivers/infiniband/ulp/rtrs/rtrs-clt-sysfs.c uses > > strncasecmp to check that the input via sysfs is "mi". But it would > > work even-if the input is "min-wrongcommand". > > And also drivers/pnp/interface.c checks "disable" command with > > strncasecmp but it would also work if the command is "disable-wrong". > > Perhaps those callers should be using strcasecmp then, rather than > strncasecmp? > > Also, if they're being liberal in accepting either case, I don't see > why the sysfs nodes should be strict in rejecting trailing input at > that point. > strcasecmp does not work when a user inputs the command with echo. We can force the human to use 'echo -n' but there are also some applications that pass the command with \n. If the command includes \n, strcasecmp does not work. In short, I need a function working well for both case-insensitive string and a string followed by '\n'. I am not native speaker of English. I think the below example can show my problem. Below is the original code. That code does not work because of the \n in the command. char buf[] = "mi\n"; if (strcasecmp(buf, "min-inflight") == 0 || strcasecmp(buf, "mi") == 0) printf("inflight\n"); else if (strcasecmp(buf, "min-latency") == 0 || strcasecmp(buf, "ml") == 0) printf("latency\n"); else printf("wrong\n"); Below is the current code in RTRS module. We replaced strcasecmp with strncasecmp. That works well but ugly and error-prone. size_t len = 0; len = strlen(buf); if (buf[len - 1] == '\n') len--; if (strncasecmp(buf, "min-inflight", 12) == 0 || (len == 2 && strncasecmp(buf, "mi", 2) == 0)) printf("inflight\n"); else if (strncasecmp(buf, "min-latency", 11) == 0 || (len == 2 && strncasecmp(buf, "ml", 2)) == 0) printf("latency\n"); else printf("wrong\n"); I think sysfs_streqcase could be the best option as below. if (sysfs_streqcase(buf, "min-inflight") || sysfs_streqcase(buf, "mi")) printf("inflight\n"); else if (sysfs_streqcase(buf, "min-latency") || sysfs_streqcase(buf, "ml")) printf("latency\n"); else printf("wrong\n"); I think that case is not my own problem. I think some code handling debugfs and sysfs also have the same problem. > > This should be declared in > include/linux/string.h > in order for others to use this (as 0day bot notes). Thank you for the kind review. I will add the declaration if I get the positive feedback for sysfs_streqcase. > > > + > > /** > > * match_string - matches given string in an array > > * @array: array of strings > > -- > > 2.25.1 > > > > > -- > Thanks, > ~Nick Desaulniers