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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: CC333180009 X-Stat-Signature: ektkq4rz7nmyxf6816nhgb4a8ba9jrj6 X-Rspam-User: X-HE-Tag: 1756704522-569478 X-HE-Meta: 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 9sKHWGhT mx3s3UapNxWrqrRwZRDyJYuMk9wiGVQfjuf+3ERgnHggcSdIQI1s6EV35mmrE2Vz+x4koh73v75picJavkKP3p0cASqWe2wcVW3/v1D3tfS3+n3mbwr4Q794QB7QSK+1rxwao8WLC0NKvZikBHeS6wnir1j3S7yo+WZwHitIURF2E9c2Ini88LbGMYR24nKc6xgq86iT7dadKTrEBebztmYZyWbWCJduHYroLkSOGljuVifEZJ7jDgl/AoTKtOtb4pF6lA34ghYkiiTMF1Xg2arKYe0W25E9zsT0Ey1TmcULhABObgRml/Bmh3KLbd6mscrbo4+OPcb/KER/8jfI9N3+kq0qzWIbU0cmTMeLpr7X7R3Z+bUZodgngKbDanfj9+TPCe21xD2VjmB3PZjZdJAWWiw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Kees, On 8/25/25 7:31 PM, Kees Cook wrote: > On Thu, Aug 21, 2025 at 03:51:51PM +0530, Bhupesh wrote: >> As Linus mentioned in [1], currently we have several memcpy() use-cases >> which use 'current->comm' to copy the task name over to local copies. >> For an example: >> >> ... >> char comm[TASK_COMM_LEN]; >> memcpy(comm, current->comm, TASK_COMM_LEN); >> ... >> >> These should be rather calling a wrappper like "get_task_array()", >> which is implemented as: >> >> static __always_inline void >> __cstr_array_copy(char *dst, >> const char *src, __kernel_size_t size) >> { >> memcpy(dst, src, size); >> dst[size] = 0; >> } >> >> #define get_task_array(dst,src) \ >> __cstr_array_copy(dst, src, __must_be_array(dst)) >> >> The relevant 'memcpy()' users were identified using the following search >> pattern: >> $ git grep 'memcpy.*->comm\>' >> >> Link:https://lore.kernel.org/all/CAHk-=wi5c=_-FBGo_88CowJd_F-Gi6Ud9d=TALm65ReN7YjrMw@mail.gmail.com/ #1 >> >> Signed-off-by: Bhupesh >> --- >> include/linux/coredump.h | 2 +- >> include/linux/sched.h | 32 +++++++++++++++++++ >> include/linux/tracepoint.h | 4 +-- >> include/trace/events/block.h | 10 +++--- >> include/trace/events/oom.h | 2 +- >> include/trace/events/osnoise.h | 2 +- >> include/trace/events/sched.h | 13 ++++---- >> include/trace/events/signal.h | 2 +- >> include/trace/events/task.h | 4 +-- >> tools/bpf/bpftool/pids.c | 6 ++-- >> .../bpf/test_kmods/bpf_testmod-events.h | 2 +- >> 11 files changed, 54 insertions(+), 25 deletions(-) >> >> diff --git a/include/linux/coredump.h b/include/linux/coredump.h >> index 68861da4cf7c..bcee0afc5eaf 100644 >> --- a/include/linux/coredump.h >> +++ b/include/linux/coredump.h >> @@ -54,7 +54,7 @@ extern void vfs_coredump(const kernel_siginfo_t *siginfo); >> do { \ >> char comm[TASK_COMM_LEN]; \ >> /* This will always be NUL terminated. */ \ >> - memcpy(comm, current->comm, sizeof(comm)); \ >> + get_task_array(comm, current->comm); \ >> printk_ratelimited(Level "coredump: %d(%*pE): " Format "\n", \ >> task_tgid_vnr(current), (int)strlen(comm), comm, ##__VA_ARGS__); \ >> } while (0) \ >> diff --git a/include/linux/sched.h b/include/linux/sched.h >> index 5a58c1270474..d26d1dfb9904 100644 >> --- a/include/linux/sched.h >> +++ b/include/linux/sched.h >> @@ -1960,12 +1960,44 @@ extern void wake_up_new_task(struct task_struct *tsk); >> >> extern void kick_process(struct task_struct *tsk); >> >> +/* >> + * - Why not use task_lock()? >> + * User space can randomly change their names anyway, so locking for readers >> + * doesn't make sense. For writers, locking is probably necessary, as a race >> + * condition could lead to long-term mixed results. >> + * The logic inside __set_task_comm() should ensure that the task comm is >> + * always NUL-terminated and zero-padded. Therefore the race condition between >> + * reader and writer is not an issue. >> + */ >> + >> extern void __set_task_comm(struct task_struct *tsk, const char *from, bool exec); >> #define set_task_comm(tsk, from) ({ \ >> BUILD_BUG_ON(sizeof(from) < TASK_COMM_LEN); \ >> __set_task_comm(tsk, from, false); \ >> }) >> >> +/* >> + * 'get_task_array' can be 'data-racy' in the destination and >> + * should not be used for cases where a 'stable NUL at the end' >> + * is needed. Its better to use strscpy and friends for such >> + * use-cases. >> + * >> + * It is suited mainly for a 'just copy comm to a constant-sized >> + * array' case - especially in performance sensitive use-cases, >> + * like tracing. >> + */ >> + >> +static __always_inline void >> + __cstr_array_copy(char *dst, const char *src, >> + __kernel_size_t size) >> +{ >> + memcpy(dst, src, size); >> + dst[size] = 0; >> +} > Please don't reinvent the wheel. :) We already have memtostr, please use > that (or memtostr_pad). Sure, but wouldn't we get a static assertion failure: "must be array" for memtostr() usage, because of the following: #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]) + __must_be_array(arr)) I think it would be easier just to set: memcpy(dst, src, size); dst[size -1] = 0; instead as Linus and Steven suggested. Thanks, Bhupesh >> + >> +#define get_task_array(dst, src) \ >> + __cstr_array_copy(dst, src, __must_be_array(dst)) > Uh, __must_be_array(dst) returns 0 on success. :P Are you sure you > tested this? >