Re: [Crash-utility] [PATCH] fix "ps -a" for tasks whose arg_start was moved

When a task used prctl(PR_SET_MM, PR_SET_MM_ARG_{START,END}, ...) (e.g. the systemd's child "(sd-pam)" in Fedora), the "ps -a" option could fail with "ps: cannot allocate any more memory!".

# ./crash -d 1 ... crash> ps -a 1591 ... PID: 1591 TASK: ffff9c7077d7b1c0 CPU: 1 COMMAND: "(sd-pam)" arg_start: 7f2f544de000 arg_end: 7f2f544de009 (9) env_start: 7ffcff12af88 env_end: 7ffcff12afdf (87) ... smallest: 16 largest: 883333320672 embedded: 2 max_embedded: 3 mallocs: 22 frees: 22 reqs/total: 912/1766672402731 average size: 1937140792 ps: cannot allocate any more memory! This happens because it assumes that the ranges of arg and env are contiguous. buf = GETBUF(env_end - arg_start + 1); This patch devides the GETBUF() into two times for arg and env. Signed-off-by: Kazuhito Hagio <k-hagio(a)ab.jp.nec.com&gt; --- task.c | 94 +++++++++++++++++++++++++++++++++++++----------------------------- 1 file changed, 53 insertions(+), 41 deletions(-) diff --git a/task.c b/task.c index 2418e4c..55242c5 100644 --- a/task.c +++ b/task.c @@ -3865,6 +3865,44 @@ show_milliseconds(struct task_context *tc, struct psinfo *psi) } } +static char * +read_arg_string(struct task_context *tc, char *buf, ulong start, ulong end) +{ + physaddr_t paddr; + ulong uvaddr, size, cnt; + char *bufptr; + + uvaddr = start; + size = end - start; + bufptr = buf; + + while (size > 0) { + if (!uvtop(tc, uvaddr, &paddr, 0)) { + error(INFO, "cannot access user stack address: %lx\n\n", + uvaddr); + return NULL; + } + + cnt = PAGESIZE() - PAGEOFFSET(uvaddr); + + if (cnt > size) + cnt = size; + + if (!readmem(paddr, PHYSADDR, bufptr, cnt, + "user stack contents", RETURN_ON_ERROR|QUIET)) { + error(INFO, "cannot access user stack address: %lx\n\n", + uvaddr); + return NULL; + } + + uvaddr += cnt; + bufptr += cnt; + size -= cnt; + } + + return bufptr; +} + /* * Show the argv and envp strings pointed to by mm_struct->arg_start * and mm_struct->env_start. The user addresses need to broken up @@ -3875,10 +3913,7 @@ static void show_task_args(struct task_context *tc) { ulong arg_start, arg_end, env_start, env_end; - char *buf, *bufptr, *p1; - char *as, *ae, *es, *ee; - physaddr_t paddr; - ulong uvaddr, size, cnt; + char *buf, *p1, *end; int c, d; print_task_header(fp, tc, 0); @@ -3910,43 +3945,13 @@ show_task_args(struct task_context *tc) env_start, env_end, env_end - env_start); } - buf = GETBUF(env_end - arg_start + 1); - - uvaddr = arg_start; - size = env_end - arg_start; - bufptr = buf; - - while (size > 0) { - if (!uvtop(tc, uvaddr, &paddr, 0)) { - error(INFO, "cannot access user stack address: %lx\n\n", - uvaddr); - goto bailout; - } - - cnt = PAGESIZE() - PAGEOFFSET(uvaddr); - - if (cnt > size) - cnt = size; - - if (!readmem(paddr, PHYSADDR, bufptr, cnt, - "user stack contents", RETURN_ON_ERROR|QUIET)) { - error(INFO, "cannot access user stack address: %lx\n\n", - uvaddr); - goto bailout; - } - - uvaddr += cnt; - bufptr += cnt; - size -= cnt; - } - - as = buf; - ae = &buf[arg_end - arg_start]; - es = &buf[env_start - arg_start]; - ee = &buf[env_end - arg_start]; + buf = GETBUF(arg_end - arg_start + 1); + end = read_arg_string(tc, buf, arg_start, arg_end); + if (!end) + goto bailout; fprintf(fp, "ARG: "); - for (p1 = as, c = 0; p1 < ae; p1++) { + for (p1 = buf, c = 0; p1 < end; p1++) { if (*p1 == NULLCHAR) { if (c) fprintf(fp, " "); @@ -3957,14 +3962,21 @@ show_task_args(struct task_context *tc) } } + FREEBUF(buf); + + buf = GETBUF(env_end - env_start + 1); + end = read_arg_string(tc, buf, env_start, env_end); + if (!end) + goto bailout; + fprintf(fp, "\nENV: "); - for (p1 = es, c = d = 0; p1 < ee; p1++) { + for (p1 = buf, c = d = 0; p1 < end; p1++) { if (*p1 == NULLCHAR) { if (c) fprintf(fp, "\n"); c = 0; } else { - fprintf(fp, "%s%c", !c && (p1 != es) ? " " : "", *p1); + fprintf(fp, "%s%c", !c && (p1 != buf) ? " " : "", *p1); c++, d++; } } -- 1.8.3.1 -- Crash-utility mailing list Crash-utility(a)redhat.com https://www.redhat.com/mailman/listinfo/crash-utility