| Message ID | 1513654094-16832-3-git-send-email-me@tobin.cc |
|---|---|
| State | Not Applicable, archived |
| Delegated to: | David Miller |
| Headers | show |
| Series | kallsyms: don't leak address | expand |
On Tue, 2017-12-19 at 14:28 +1100, Tobin C. Harding wrote: > Depends on: commit 40eee173a35e ("kallsyms: don't leak address when > symbol not found") > > Currently vsprintf for specifiers %p[SsB] relies on the behaviour of > kallsyms (sprint_symbol()) and prints the actual address if a symbol is > not found. Previous patch changes this behaviour so that sprint_symbol() > returns an error if symbol not found. With this patch in place we can > print a sanitized message '<symbol not found>' instead of leaking the > address. > > Print '<symbol not found>' for printk specifier %p[sSB] if symbol look > up fails. > > Signed-off-by: Tobin C. Harding <me@tobin.cc> > --- > lib/vsprintf.c | 11 ++++++++--- > 1 file changed, 8 insertions(+), 3 deletions(-) > > diff --git a/lib/vsprintf.c b/lib/vsprintf.c > index 01c3957b2de6..820ed4fe6e6c 100644 > --- a/lib/vsprintf.c > +++ b/lib/vsprintf.c > @@ -674,6 +674,8 @@ char *symbol_string(char *buf, char *end, void *ptr, > unsigned long value; > #ifdef CONFIG_KALLSYMS > char sym[KSYM_SYMBOL_LEN]; > + const char *sym_not_found = "<symbol not found>"; This will be reinitialized on every use. > + int ret; > #endif > > if (fmt[1] == 'R') > @@ -682,11 +684,14 @@ char *symbol_string(char *buf, char *end, void *ptr, > > #ifdef CONFIG_KALLSYMS > if (*fmt == 'B') > - sprint_backtrace(sym, value); > + ret = sprint_backtrace(sym, value); > else if (*fmt != 'f' && *fmt != 's') > - sprint_symbol(sym, value); > + ret = sprint_symbol(sym, value); > else > - sprint_symbol_no_offset(sym, value); > + ret = sprint_symbol_no_offset(sym, value); > + > + if (ret == -1) > + strcpy(sym, sym_not_found); This could avoid the unnecessary strcpy if sym_not_found was not used at all and this was used instead if (ret == -1) return string(buf, end, "<symbol not found>", spec); return string(buf, end, sym, spec); or maybe return string(buf, end, ret == -1 ? "<symbol not found>" : sum, spec); > > return string(buf, end, sym, spec); > #else
On Mon, Dec 18, 2017 at 10:18:27PM -0800, Joe Perches wrote: > On Tue, 2017-12-19 at 14:28 +1100, Tobin C. Harding wrote: > > Depends on: commit 40eee173a35e ("kallsyms: don't leak address when > > symbol not found") > > > > Currently vsprintf for specifiers %p[SsB] relies on the behaviour of > > kallsyms (sprint_symbol()) and prints the actual address if a symbol is > > not found. Previous patch changes this behaviour so that sprint_symbol() > > returns an error if symbol not found. With this patch in place we can > > print a sanitized message '<symbol not found>' instead of leaking the > > address. > > > > Print '<symbol not found>' for printk specifier %p[sSB] if symbol look > > up fails. > > > > Signed-off-by: Tobin C. Harding <me@tobin.cc> > > --- > > lib/vsprintf.c | 11 ++++++++--- > > 1 file changed, 8 insertions(+), 3 deletions(-) > > > > diff --git a/lib/vsprintf.c b/lib/vsprintf.c > > index 01c3957b2de6..820ed4fe6e6c 100644 > > --- a/lib/vsprintf.c > > +++ b/lib/vsprintf.c > > @@ -674,6 +674,8 @@ char *symbol_string(char *buf, char *end, void *ptr, > > unsigned long value; > > #ifdef CONFIG_KALLSYMS > > char sym[KSYM_SYMBOL_LEN]; > > + const char *sym_not_found = "<symbol not found>"; > > This will be reinitialized on every use. > > > + int ret; > > #endif > > > > if (fmt[1] == 'R') > > @@ -682,11 +684,14 @@ char *symbol_string(char *buf, char *end, void *ptr, > > > > #ifdef CONFIG_KALLSYMS > > if (*fmt == 'B') > > - sprint_backtrace(sym, value); > > + ret = sprint_backtrace(sym, value); > > else if (*fmt != 'f' && *fmt != 's') > > - sprint_symbol(sym, value); > > + ret = sprint_symbol(sym, value); > > else > > - sprint_symbol_no_offset(sym, value); > > + ret = sprint_symbol_no_offset(sym, value); > > + > > + if (ret == -1) > > + strcpy(sym, sym_not_found); > > > This could avoid the unnecessary strcpy if sym_not_found > was not used at all and this was used instead > > if (ret == -1) > return string(buf, end, "<symbol not found>", spec); > > return string(buf, end, sym, spec); > > or maybe > > return string(buf, end, ret == -1 ? "<symbol not found>" : sum, spec); Oh, thanks. This is much cleaner. Will re-spin. thanks, Tobin.
diff --git a/lib/vsprintf.c b/lib/vsprintf.c index 01c3957b2de6..820ed4fe6e6c 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -674,6 +674,8 @@ char *symbol_string(char *buf, char *end, void *ptr, unsigned long value; #ifdef CONFIG_KALLSYMS char sym[KSYM_SYMBOL_LEN]; + const char *sym_not_found = "<symbol not found>"; + int ret; #endif if (fmt[1] == 'R') @@ -682,11 +684,14 @@ char *symbol_string(char *buf, char *end, void *ptr, #ifdef CONFIG_KALLSYMS if (*fmt == 'B') - sprint_backtrace(sym, value); + ret = sprint_backtrace(sym, value); else if (*fmt != 'f' && *fmt != 's') - sprint_symbol(sym, value); + ret = sprint_symbol(sym, value); else - sprint_symbol_no_offset(sym, value); + ret = sprint_symbol_no_offset(sym, value); + + if (ret == -1) + strcpy(sym, sym_not_found); return string(buf, end, sym, spec); #else
Depends on: commit 40eee173a35e ("kallsyms: don't leak address when symbol not found") Currently vsprintf for specifiers %p[SsB] relies on the behaviour of kallsyms (sprint_symbol()) and prints the actual address if a symbol is not found. Previous patch changes this behaviour so that sprint_symbol() returns an error if symbol not found. With this patch in place we can print a sanitized message '<symbol not found>' instead of leaking the address. Print '<symbol not found>' for printk specifier %p[sSB] if symbol look up fails. Signed-off-by: Tobin C. Harding <me@tobin.cc> --- lib/vsprintf.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-)