Set maximum file descriptor number limit by rlimit.rlim_max than nr_open(hard limit). Hard limit may cause dup2 fail.
Signed-off-by: lufei lufei@uniontech.com --- tools/testing/selftests/core/unshare_test.c | 24 ++++++++++++++------- 1 file changed, 16 insertions(+), 8 deletions(-)
diff --git a/tools/testing/selftests/core/unshare_test.c b/tools/testing/selftests/core/unshare_test.c index 7fec9dfb1b0e..66b651168887 100644 --- a/tools/testing/selftests/core/unshare_test.c +++ b/tools/testing/selftests/core/unshare_test.c @@ -30,6 +30,7 @@ TEST(unshare_EMFILE) static char buf[512], buf2[512]; struct rlimit rlimit; int nr_open; + int rlimit_max;
fd = open("/proc/sys/fs/nr_open", O_RDWR); ASSERT_GE(fd, 0); @@ -42,22 +43,24 @@ TEST(unshare_EMFILE)
ASSERT_EQ(0, getrlimit(RLIMIT_NOFILE, &rlimit));
- /* bump fs.nr_open */ - n2 = sprintf(buf2, "%d\n", nr_open + 1024); + rlimit_max = rlimit.rlim_max; + + /* bump rlimit.rlim_max */ + n2 = sprintf(buf2, "%d\n", rlimit_max + 1024); lseek(fd, 0, SEEK_SET); write(fd, buf2, n2);
/* bump ulimit -n */ - rlimit.rlim_cur = nr_open + 1024; - rlimit.rlim_max = nr_open + 1024; + rlimit.rlim_cur = rlimit_max + 1024; + rlimit.rlim_max = rlimit_max + 1024; EXPECT_EQ(0, setrlimit(RLIMIT_NOFILE, &rlimit)) { lseek(fd, 0, SEEK_SET); write(fd, buf, n); exit(EXIT_FAILURE); }
- /* get a descriptor past the old fs.nr_open */ - EXPECT_GE(dup2(2, nr_open + 64), 0) { + /* get a descriptor past the old rlimit.rlim_max */ + EXPECT_GE(dup2(2, rlimit_max + 64), 0) { lseek(fd, 0, SEEK_SET); write(fd, buf, n); exit(EXIT_FAILURE); @@ -74,15 +77,20 @@ TEST(unshare_EMFILE) if (pid == 0) { int err;
- /* restore fs.nr_open */ + n2 = sprintf(buf2, "%d\n", rlimit_max); lseek(fd, 0, SEEK_SET); - write(fd, buf, n); + write(fd, buf2, n2); + /* ... and now unshare(CLONE_FILES) must fail with EMFILE */ err = unshare(CLONE_FILES); EXPECT_EQ(err, -1) exit(EXIT_FAILURE); EXPECT_EQ(errno, EMFILE) exit(EXIT_FAILURE); + + /* restore fs.nr_open */ + lseek(fd, 0, SEEK_SET); + write(fd, buf, n); exit(EXIT_SUCCESS); }
On 3/31/25 19:55, lufei wrote:
Set maximum file descriptor number limit by rlimit.rlim_max than nr_open(hard limit). Hard limit may cause dup2 fail.
Signed-off-by: lufei lufei@uniontech.com
Petr, Al,
Okay to take this patch?
thanks, -- Shuah
On 3/31/25 19:55, lufei wrote:
Set maximum file descriptor number limit by rlimit.rlim_max than nr_open(hard limit). Hard limit may cause dup2 fail.
Signed-off-by: lufei lufei@uniontech.com
Petr, Al,
Okay to take this patch?
LGTM, hopefully I haven't overlook anything.
Reviewed-by: Petr Vorel pvorel@suse.cz
FYI Cyril Hrubis suggested a different approach (for LTP tests which is based on this Al's test):
https://lore.kernel.org/ltp/Z-u7yYJpTBG8Hi6A@yuki.lan/ https://lore.kernel.org/ltp/Z-vwYZxLms8juTjX@yuki.lan/
filedescriptor that is >= 64 and set the nr_open to 64.
That would help to avoid using /proc/sys/fs/nr_open.
Kind regards, Petr
thanks, -- Shuah
On 4/8/25 23:56, Petr Vorel wrote:
On 3/31/25 19:55, lufei wrote:
Set maximum file descriptor number limit by rlimit.rlim_max than nr_open(hard limit). Hard limit may cause dup2 fail.
Signed-off-by: lufei lufei@uniontech.com
Petr, Al,
Okay to take this patch?
LGTM, hopefully I haven't overlook anything.
Reviewed-by: Petr Vorel pvorel@suse.cz
FYI Cyril Hrubis suggested a different approach (for LTP tests which is based on this Al's test):
https://lore.kernel.org/ltp/Z-u7yYJpTBG8Hi6A@yuki.lan/ https://lore.kernel.org/ltp/Z-vwYZxLms8juTjX@yuki.lan/
filedescriptor that is >= 64 and set the nr_open to 64.
That would help to avoid using /proc/sys/fs/nr_open.
Thank you for this suggestion.
lufei, Can you look into this as a solution? Also the short log should include the subsystem: e.:
selftests:core: unshare_test: -----
thanks, -- Shuah
On Wed, Apr 09, 2025 at 03:30:32PM -0600, Shuah Khan wrote:
On 4/8/25 23:56, Petr Vorel wrote:
On 3/31/25 19:55, lufei wrote:
Set maximum file descriptor number limit by rlimit.rlim_max than nr_open(hard limit). Hard limit may cause dup2 fail.
Signed-off-by: lufei lufei@uniontech.com
Petr, Al,
Okay to take this patch?
LGTM, hopefully I haven't overlook anything.
Reviewed-by: Petr Vorel pvorel@suse.cz
FYI Cyril Hrubis suggested a different approach (for LTP tests which is based on this Al's test):
https://lore.kernel.org/ltp/Z-u7yYJpTBG8Hi6A@yuki.lan/ https://lore.kernel.org/ltp/Z-vwYZxLms8juTjX@yuki.lan/
filedescriptor that is >= 64 and set the nr_open to 64.
That would help to avoid using /proc/sys/fs/nr_open.
Thank you for this suggestion.
lufei, Can you look into this as a solution? Also the short log should include the subsystem: e.:
selftests:core: unshare_test: -----
thanks, -- Shuah
Hi Shuah,
Thanks very much for reply.
I'll submit a v3 patch with dup a filedescriptor >= sizeof(long)*8 and set nr_open to sizeof(long)*8 to trigger EMFILE.
Hi Petr, Shuah, I don't have a i686 environment, only on x86_64 has been tested. Is this all right?
I'll re-write short log as asked in v3 patch.
dup2(2, nr_open+64) may cause ENOMEM error, change to dup2(2, bits_per_long +1) and set nr_open to bits_per_long to avoid ENOMEM.
Signed-off-by: lufei lufei@uniontech.com --- tools/testing/selftests/core/unshare_test.c | 32 +++++++-------------- 1 file changed, 11 insertions(+), 21 deletions(-)
diff --git a/tools/testing/selftests/core/unshare_test.c b/tools/testing/selftests/core/unshare_test.c index 7fec9dfb1b0e..ea4caa7ec28d 100644 --- a/tools/testing/selftests/core/unshare_test.c +++ b/tools/testing/selftests/core/unshare_test.c @@ -28,8 +28,8 @@ TEST(unshare_EMFILE) int fd; ssize_t n, n2; static char buf[512], buf2[512]; - struct rlimit rlimit; int nr_open; + int bits_per_long = sizeof(long) * 8;
fd = open("/proc/sys/fs/nr_open", O_RDWR); ASSERT_GE(fd, 0); @@ -40,24 +40,8 @@ TEST(unshare_EMFILE)
ASSERT_EQ(sscanf(buf, "%d", &nr_open), 1);
- ASSERT_EQ(0, getrlimit(RLIMIT_NOFILE, &rlimit)); - - /* bump fs.nr_open */ - n2 = sprintf(buf2, "%d\n", nr_open + 1024); - lseek(fd, 0, SEEK_SET); - write(fd, buf2, n2); - - /* bump ulimit -n */ - rlimit.rlim_cur = nr_open + 1024; - rlimit.rlim_max = nr_open + 1024; - EXPECT_EQ(0, setrlimit(RLIMIT_NOFILE, &rlimit)) { - lseek(fd, 0, SEEK_SET); - write(fd, buf, n); - exit(EXIT_FAILURE); - } - - /* get a descriptor past the old fs.nr_open */ - EXPECT_GE(dup2(2, nr_open + 64), 0) { + /* get a descriptor >= bits_per_long */ + EXPECT_GE(dup2(2, bits_per_long+1), 0) { lseek(fd, 0, SEEK_SET); write(fd, buf, n); exit(EXIT_FAILURE); @@ -74,15 +58,21 @@ TEST(unshare_EMFILE) if (pid == 0) { int err;
- /* restore fs.nr_open */ + /* set nr_open == bits_per_long */ + n2 = sprintf(buf2, "%d\n", bits_per_long); lseek(fd, 0, SEEK_SET); - write(fd, buf, n); + write(fd, buf2, n2); + /* ... and now unshare(CLONE_FILES) must fail with EMFILE */ err = unshare(CLONE_FILES); EXPECT_EQ(err, -1) exit(EXIT_FAILURE); EXPECT_EQ(errno, EMFILE) exit(EXIT_FAILURE); + + /* restore fs.nr_open */ + lseek(fd, 0, SEEK_SET); + write(fd, buf, n); exit(EXIT_SUCCESS); }
linux-kselftest-mirror@lists.linaro.org
-
Lu Fei -
lufei
-
Petr Vorel -
Shuah Khan