Messages in this thread Patch in this message | | | From | Artem Savkov <> | Subject | [PATCH v3 2/2] objtool: fix .cold functions parent symbols search | Date | Mon, 12 Nov 2018 13:55:19 +0100 |
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Because find_symbol_by_name() traverses the same lists as read_symbols() changing sym->name in place without copying it affects the result of find_symbol_by_name() and, in case when ".cold" function precedes it's parent in sec->symbol_list, can result in function being considered a parent of itself. This leads to function length being set to 0 and other consequent side-effects including a segfault in add_switch_table(). The effects of this bug are only visible when building with -ffunction-sections in KCFLAGS.
Fix by copying the search string instead of modifying it in place.
Fixes: 13810435b9a7 "objtool: Support GCC 8's cold subfunctions" Signed-off-by: Artem Savkov <asavkov@redhat.com> --- tools/objtool/elf.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-)
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c index 3decd43477df..15d9acfb2c97 100644 --- a/tools/objtool/elf.c +++ b/tools/objtool/elf.c @@ -31,6 +31,8 @@ #include "elf.h" #include "warn.h" +#define MAX_NAME_LEN 128 + struct section *find_section_by_name(struct elf *elf, const char *name) { struct section *sec; @@ -298,6 +300,8 @@ static int read_symbols(struct elf *elf) /* Create parent/child links for any cold subfunctions */ list_for_each_entry(sec, &elf->sections, list) { list_for_each_entry(sym, &sec->symbol_list, list) { + char pname[MAX_NAME_LEN + 1]; + size_t pnamelen; if (sym->type != STT_FUNC) continue; sym->pfunc = sym->cfunc = sym; @@ -305,9 +309,16 @@ static int read_symbols(struct elf *elf) if (!coldstr) continue; - coldstr[0] = '\0'; - pfunc = find_symbol_by_name(elf, sym->name); - coldstr[0] = '.'; + pnamelen = coldstr - sym->name; + if (pnamelen > MAX_NAME_LEN) { + WARN("%s(): parent function name exceeds maximum length of %d characters", + sym->name, MAX_NAME_LEN); + goto cold_err; + } + + strncpy(pname, sym->name, pnamelen); + pname[pnamelen] = '\0'; + pfunc = find_symbol_by_name(elf, pname); if (!pfunc) { WARN("%s(): can't find parent function", -- 2.17.2
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