kernel/git/next/linux-next.git/tools/perf/util/machine.c, branch master

perf thread: Fix live-session detection in thread__e_machine()

2026-09-08T21:08:37+00:00

When the per-thread e_machine cannot be determined from the DSOs in the thread's maps, thread__e_machine_endian() decides between reading /proc//exe and falling back to the recorded session environment: bool is_live = machine->machines == NULL; if (!is_live) { /* Check if the session has a data file. */ struct perf_session *session = container_of(...); is_live = !!session->data; } Neither half of that works. The back pointer added by commit a088031c4998 ("perf tools: Add machine to machines back pointer") is set by machines__add(), which only ever adds guests; the host machine never gets one. Host-machine threads, which is to say almost all of them, therefore see machine->machines == NULL and are declared live before the session is consulted at all. The session test is also inverted. A session with a perf_data attached is one being read from a perf.data file, i.e. exactly the case that is not live, while a live session such as 'perf top' passes data=NULL to __perf_session__new(). So a file-based session takes the live path and reads /proc//exe on the analysing host, which at best describes an unrelated process that has since been given the recorded pid, and normally just fails, leaving e_machine as EM_NONE. The perf_env fallback that would have supplied the recorded architecture is never reached, and thread__e_machine() returns EM_HOST. For a same-architecture recording this is invisible, since EM_HOST is the right answer anyway. Cross-architecture it is not: annotating an Alpha perf.data on an x86_64 host selects the x86 struct arch, so the Alpha disassembly is matched against the x86 instruction table. Alpha's 'ret' collides with x86's and gets ret_ops, while its calls and branches match nothing and are left unparsed, so no call target is resolved and no jump arrows are drawn. Set the back pointer for the host machine and correct the session test. The new back pointer does not disturb the other reader of the field, machine__findnew_guest_code(), which machine__resolve() only calls when !machine__is_host(machine). Fixes: 70351029b55677eb ("perf thread: Add support for reading the e_machine type for a thread") Reviewed-by: Ian Rogers Signed-off-by: Matt Turner Cc: Namhyung Kim Signed-off-by: Arnaldo Carvalho de Melo

perf machine: Check snprintf truncation for guest kallsyms path

2026-07-31T23:42:28+00:00

machines__create_guest_kernel_maps() builds the guest kallsyms path with snprintf() without checking the return value. A truncated path could pass the access() check if a prefix directory happens to contain a file named "kallsyms", leading to the wrong file being used for symbol resolution. Check for truncation and skip the directory. Fixes: a1645ce12adb ("perf: 'perf kvm' tool for monitoring guest performance from host") Reported-by: sashiko-bot Cc: Zhang, Yanmin Assisted-by: Claude:claude-opus-4.6 Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: Namhyung Kim

perf machine: Free scandir entries in guest kernel map creation

2026-07-31T23:42:17+00:00

machines__create_guest_kernel_maps() calls scandir() which allocates both the namelist array and each individual dirent entry. The code frees the namelist array but not the individual entries, leaking memory proportional to the number of directories under guestmount. Free each namelist[i] after it is no longer needed. Fixes: a1645ce12adb ("perf: 'perf kvm' tool for monitoring guest performance from host") Reported-by: sashiko-bot Cc: Zhang, Yanmin Assisted-by: Claude:claude-opus-4.6 Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: Namhyung Kim

perf machine: Reset errno before strtol in guest kernel map creation

2026-07-31T23:42:07+00:00

machines__create_guest_kernel_maps() checks errno == ERANGE after strtol() to detect overflow, but does not clear errno first. A stale ERANGE from an earlier library call (e.g. scandir internals) causes valid numeric directory names to be incorrectly skipped. Set errno = 0 before strtol() so only the current conversion can trigger the ERANGE check. Fixes: a1645ce12adb ("perf: 'perf kvm' tool for monitoring guest performance from host") Reported-by: sashiko-bot Cc: Zhang, Yanmin Assisted-by: Claude:claude-opus-4.6 Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: Namhyung Kim

perf machine: Don't abort guest map creation on first inaccessible dir

2026-07-31T23:41:56+00:00

machines__create_guest_kernel_maps() jumps to the failure label when one guest directory's kallsyms file fails access(), skipping all remaining valid guest directories. An inaccessible directory is not fatal — other guests may still be reachable. Replace 'goto failure' with 'continue' so the loop processes all directories, and remove the now-unreferenced failure label. Fixes: a1645ce12adb ("perf: 'perf kvm' tool for monitoring guest performance from host") Reported-by: sashiko-bot Cc: Zhang, Yanmin Assisted-by: Claude:claude-opus-4.6 Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: Namhyung Kim

perf machine: Check snprintf truncation in machines__findnew()

2026-07-31T23:41:41+00:00

The guestmount path is built with snprintf() into a PATH_MAX buffer without checking the return value. If symbol_conf.guestmount is long enough to cause truncation, the truncated path could match a different directory, causing the wrong guest to be associated with the pid. Check for truncation and bail out early. Fixes: a1645ce12adb ("perf: 'perf kvm' tool for monitoring guest performance from host") Reported-by: sashiko-bot Cc: Zhang, Yanmin Assisted-by: Claude:claude-opus-4.6 Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: Namhyung Kim

perf machine: Guard against NULL strlist in machines__findnew()

2026-07-31T23:41:38+00:00

The static 'seen' strlist caches guestmount paths that have already been reported as inaccessible, to avoid repeating the error message. If strlist__new() fails (OOM), 'seen' stays NULL and the next call dereferences it via strlist__has_entry() and strlist__add(). Guard both calls so that on allocation failure the error message is still printed (just not deduplicated) instead of crashing. Fixes: c80c3c269011 ("perf kvm: Limit repetitive guestmount message to once per directory") Reported-by: sashiko-bot Cc: David Ahern Assisted-by: Claude:claude-opus-4.6 Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: Namhyung Kim

perf machine: Fix NULL parent dereference in fork event processing

2026-07-31T23:41:35+00:00

machine__process_fork_event() calls machine__findnew_thread() for the parent thread, which can return NULL on allocation failure. The code then dereferences parent via thread__pid(parent) without a NULL check when validating whether the parent PID matches. The later NULL check at thread__fork() does not prevent this earlier dereference. Add a NULL guard before accessing the parent thread. Fixes: 5cb73340d92a ("perf tools: Make fork event processing more resilient") Reported-by: sashiko-bot Cc: Adrian Hunter Assisted-by: Claude:claude-opus-4.6 Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: Namhyung Kim

perf machine: Fix fd leak on bounds check in maps__set_modules_path_dir()

2026-07-31T23:41:21+00:00

The bounds check for root_len >= path_size returns -1 directly without closing the directory fd opened by io_dir__init() a few lines above. Jump to the out label instead, which calls close(iod.dirfd). Fixes: e7af1946818b ("perf machine: Reuse module path buffer") Reported-by: sashiko-bot Cc: Ian Rogers Assisted-by: Claude:claude-opus-4.6 Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: Namhyung Kim

perf machine: Use snprintf() for guestmount path construction

2026-06-17T12:21:03+00:00

machines__findnew() and machines__create_guest_kernel_maps() use sprintf() to build paths by prepending symbol_conf.guestmount. Both write into PATH_MAX stack buffers, but guestmount comes from user configuration and is not length-checked. A guestmount path at or near PATH_MAX causes a stack buffer overflow. Switch to snprintf() with sizeof() to prevent overflow. The subsequent access()/fopen() calls will fail on a truncated path. Fixes: a1645ce12adb6c9c ("perf: 'perf kvm' tool for monitoring guest performance from host") Reported-by: sashiko-bot Cc: Zhang, Yanmin Assisted-by: Claude:claude-opus-4.6 Signed-off-by: Arnaldo Carvalho de Melo