Hi, On Mon, Apr 22, 2024 at 05:35:54PM +0100, Daniel Thompson wrote: > Currently, when the user attempts symbol completion with the Tab key, kdb > will use strncpy() to insert the completed symbol into the command buffer. > Unfortunately it passes the size of the source buffer rather than the > destination to strncpy() with predictably horrible results. Most obviously > if the command buffer is already full but cp, the cursor position, is in > the middle of the buffer, then we will write past the end of the supplied > buffer. > > Fix this by replacing the dubious strncpy() calls with memmove()/memcpy() > calls plus explicit boundary checks to make sure we have enough space > before we start moving characters around. > > Reported-by: Justin Stitt <justinstitt@xxxxxxxxxx> > Closes: https://lore.kernel.org/all/CAFhGd8qESuuifuHsNjFPR-Va3P80bxrw+LqvC8deA8GziUJLpw@xxxxxxxxxxxxxx/ > Cc: stable@xxxxxxxxxxxxxxx > Signed-off-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx> Nice! This is better than the conversions I tried to make earlier. Your patch helps with https://github.com/KSPP/linux/issues/90 Reviewed-by: Justin Stitt <justinstitt@xxxxxxxxxx> > --- > kernel/debug/kdb/kdb_io.c | 21 +++++++++++++-------- > 1 file changed, 13 insertions(+), 8 deletions(-) > > diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c > index 9443bc63c5a24..06dfbccb10336 100644 > --- a/kernel/debug/kdb/kdb_io.c > +++ b/kernel/debug/kdb/kdb_io.c > @@ -367,14 +367,19 @@ static char *kdb_read(char *buffer, size_t bufsize) > kdb_printf(kdb_prompt_str); > kdb_printf("%s", buffer); > } else if (tab != 2 && count > 0) { > - len_tmp = strlen(p_tmp); > - strncpy(p_tmp+len_tmp, cp, lastchar-cp+1); > - len_tmp = strlen(p_tmp); > - strncpy(cp, p_tmp+len, len_tmp-len + 1); > - len = len_tmp - len; > - kdb_printf("%s", cp); > - cp += len; > - lastchar += len; > + /* How many new characters do we want from tmpbuffer? */ > + len_tmp = strlen(p_tmp) - len; > + if (lastchar + len_tmp >= bufend) > + len_tmp = bufend - lastchar; > + > + if (len_tmp) { > + /* + 1 ensures the '\0' is memmove'd */ > + memmove(cp+len_tmp, cp, (lastchar-cp) + 1); > + memcpy(cp, p_tmp+len, len_tmp); > + kdb_printf("%s", cp); > + cp += len_tmp; > + lastchar += len_tmp; > + } > } > kdb_nextline = 1; /* reset output line number */ > break; > > -- > 2.43.0 > > Thanks Justin
