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objtool: Fix segfault in .cold detection with -ffunction-sections
[ Upstream commit22566c1603
] 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(). In the case where a ".cold" function precedes its parent in sec->symbol_list, it can result in a 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. Signed-off-by: Artem Savkov <asavkov@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Fixes:13810435b9
("objtool: Support GCC 8's cold subfunctions") Link: http://lkml.kernel.org/r/910abd6b5a4945130fd44f787c24e07b9e07c8da.1542736240.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
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1 changed files with 14 additions and 3 deletions
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@ -31,6 +31,8 @@
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#include "elf.h"
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#include "warn.h"
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#define MAX_NAME_LEN 128
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struct section *find_section_by_name(struct elf *elf, const char *name)
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{
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struct section *sec;
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@ -298,6 +300,8 @@ static int read_symbols(struct elf *elf)
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/* Create parent/child links for any cold subfunctions */
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list_for_each_entry(sec, &elf->sections, list) {
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list_for_each_entry(sym, &sec->symbol_list, list) {
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char pname[MAX_NAME_LEN + 1];
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size_t pnamelen;
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if (sym->type != STT_FUNC)
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continue;
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sym->pfunc = sym->cfunc = sym;
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@ -305,9 +309,16 @@ static int read_symbols(struct elf *elf)
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if (!coldstr)
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continue;
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coldstr[0] = '\0';
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pfunc = find_symbol_by_name(elf, sym->name);
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coldstr[0] = '.';
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pnamelen = coldstr - sym->name;
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if (pnamelen > MAX_NAME_LEN) {
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WARN("%s(): parent function name exceeds maximum length of %d characters",
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sym->name, MAX_NAME_LEN);
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return -1;
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}
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strncpy(pname, sym->name, pnamelen);
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pname[pnamelen] = '\0';
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pfunc = find_symbol_by_name(elf, pname);
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if (!pfunc) {
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WARN("%s(): can't find parent function",
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