* [PATCH 0/2] objtool: Fixes in .cold detection logic @ 2018-11-20 17:52 Josh Poimboeuf 2018-11-20 17:52 ` [PATCH 1/2] objtool: Fix double-free in .cold detection error path Josh Poimboeuf 2018-11-20 17:52 ` [PATCH 2/2] objtool: Fix seg fault in .cold detection with -ffunction-sections Josh Poimboeuf 0 siblings, 2 replies; 5+ messages in thread From: Josh Poimboeuf @ 2018-11-20 17:52 UTC (permalink / raw) To: x86; +Cc: linux-kernel, Artem Savkov, Peter Zijlstra A couple of objtool fixes from Artem Savkov. Fix a double-free in an error path, and a seg fault seen with -ffunction-sections. Artem Savkov (2): objtool: Fix double-free in .cold detection error path objtool: Fix seg fault in .cold detection with -ffunction-sections tools/objtool/elf.c | 19 +++++++++++++++---- 1 file changed, 15 insertions(+), 4 deletions(-) -- 2.17.2 ^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH 1/2] objtool: Fix double-free in .cold detection error path 2018-11-20 17:52 [PATCH 0/2] objtool: Fixes in .cold detection logic Josh Poimboeuf @ 2018-11-20 17:52 ` Josh Poimboeuf 2018-11-20 18:05 ` [tip:core/urgent] " tip-bot for Artem Savkov 2018-11-20 17:52 ` [PATCH 2/2] objtool: Fix seg fault in .cold detection with -ffunction-sections Josh Poimboeuf 1 sibling, 1 reply; 5+ messages in thread From: Josh Poimboeuf @ 2018-11-20 17:52 UTC (permalink / raw) To: x86; +Cc: linux-kernel, Artem Savkov, Peter Zijlstra From: Artem Savkov <asavkov@redhat.com> If read_symbols() fails during second list traversal (the one dealing with ".cold" subfunctions) it frees the symbol, but never deletes it from the list/hash_table resulting in symbol being freed again in elf_close(). Fix it by just returning an error, leaving cleanup to elf_close(). Fixes: 13810435b9a7 ("objtool: Support GCC 8's cold subfunctions") Signed-off-by: Artem Savkov <asavkov@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> --- tools/objtool/elf.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c index 6dbb9fae0f9d..e7a7ac40e045 100644 --- a/tools/objtool/elf.c +++ b/tools/objtool/elf.c @@ -312,7 +312,7 @@ static int read_symbols(struct elf *elf) if (!pfunc) { WARN("%s(): can't find parent function", sym->name); - goto err; + return -1; } sym->pfunc = pfunc; -- 2.17.2 ^ permalink raw reply related [flat|nested] 5+ messages in thread
* [tip:core/urgent] objtool: Fix double-free in .cold detection error path 2018-11-20 17:52 ` [PATCH 1/2] objtool: Fix double-free in .cold detection error path Josh Poimboeuf @ 2018-11-20 18:05 ` tip-bot for Artem Savkov 0 siblings, 0 replies; 5+ messages in thread From: tip-bot for Artem Savkov @ 2018-11-20 18:05 UTC (permalink / raw) To: linux-tip-commits Cc: linux-kernel, peterz, torvalds, mingo, tglx, hpa, jpoimboe, asavkov Commit-ID: 0b9301fb632f7111a3293a30cc5b20f1b82ed08d Gitweb: https://git.kernel.org/tip/0b9301fb632f7111a3293a30cc5b20f1b82ed08d Author: Artem Savkov <asavkov@redhat.com> AuthorDate: Tue, 20 Nov 2018 11:52:15 -0600 Committer: Ingo Molnar <mingo@kernel.org> CommitDate: Tue, 20 Nov 2018 18:59:00 +0100 objtool: Fix double-free in .cold detection error path If read_symbols() fails during second list traversal (the one dealing with ".cold" subfunctions) it frees the symbol, but never deletes it from the list/hash_table resulting in symbol being freed again in elf_close(). Fix it by just returning an error, leaving cleanup to elf_close(). 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: 13810435b9a7 ("objtool: Support GCC 8's cold subfunctions") Link: http://lkml.kernel.org/r/beac5a9b7da9e8be90223459dcbe07766ae437dd.1542736240.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org> --- tools/objtool/elf.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c index 6dbb9fae0f9d..e7a7ac40e045 100644 --- a/tools/objtool/elf.c +++ b/tools/objtool/elf.c @@ -312,7 +312,7 @@ static int read_symbols(struct elf *elf) if (!pfunc) { WARN("%s(): can't find parent function", sym->name); - goto err; + return -1; } sym->pfunc = pfunc; ^ permalink raw reply related [flat|nested] 5+ messages in thread
* [PATCH 2/2] objtool: Fix seg fault in .cold detection with -ffunction-sections 2018-11-20 17:52 [PATCH 0/2] objtool: Fixes in .cold detection logic Josh Poimboeuf 2018-11-20 17:52 ` [PATCH 1/2] objtool: Fix double-free in .cold detection error path Josh Poimboeuf @ 2018-11-20 17:52 ` Josh Poimboeuf 2018-11-20 18:05 ` [tip:core/urgent] objtool: Fix segfault " tip-bot for Artem Savkov 1 sibling, 1 reply; 5+ messages in thread From: Josh Poimboeuf @ 2018-11-20 17:52 UTC (permalink / raw) To: x86; +Cc: linux-kernel, Artem Savkov, Peter Zijlstra From: Artem Savkov <asavkov@redhat.com> 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. Fixes: 13810435b9a7 ("objtool: Support GCC 8's cold subfunctions") Signed-off-by: Artem Savkov <asavkov@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@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 e7a7ac40e045..b8f3cca8e58b 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); + return -1; + } + + 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 ^ permalink raw reply related [flat|nested] 5+ messages in thread
* [tip:core/urgent] objtool: Fix segfault in .cold detection with -ffunction-sections 2018-11-20 17:52 ` [PATCH 2/2] objtool: Fix seg fault in .cold detection with -ffunction-sections Josh Poimboeuf @ 2018-11-20 18:05 ` tip-bot for Artem Savkov 0 siblings, 0 replies; 5+ messages in thread From: tip-bot for Artem Savkov @ 2018-11-20 18:05 UTC (permalink / raw) To: linux-tip-commits Cc: torvalds, peterz, mingo, asavkov, hpa, linux-kernel, jpoimboe, tglx Commit-ID: 22566c1603030f0a036ad564634b064ad1a55db2 Gitweb: https://git.kernel.org/tip/22566c1603030f0a036ad564634b064ad1a55db2 Author: Artem Savkov <asavkov@redhat.com> AuthorDate: Tue, 20 Nov 2018 11:52:16 -0600 Committer: Ingo Molnar <mingo@kernel.org> CommitDate: Tue, 20 Nov 2018 18:59:00 +0100 objtool: Fix segfault in .cold detection with -ffunction-sections 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: 13810435b9a7 ("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> --- 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 e7a7ac40e045..b8f3cca8e58b 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); + return -1; + } + + strncpy(pname, sym->name, pnamelen); + pname[pnamelen] = '\0'; + pfunc = find_symbol_by_name(elf, pname); if (!pfunc) { WARN("%s(): can't find parent function", ^ permalink raw reply related [flat|nested] 5+ messages in thread
end of thread, other threads:[~2018-11-20 18:06 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2018-11-20 17:52 [PATCH 0/2] objtool: Fixes in .cold detection logic Josh Poimboeuf 2018-11-20 17:52 ` [PATCH 1/2] objtool: Fix double-free in .cold detection error path Josh Poimboeuf 2018-11-20 18:05 ` [tip:core/urgent] " tip-bot for Artem Savkov 2018-11-20 17:52 ` [PATCH 2/2] objtool: Fix seg fault in .cold detection with -ffunction-sections Josh Poimboeuf 2018-11-20 18:05 ` [tip:core/urgent] objtool: Fix segfault " tip-bot for Artem Savkov
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