user/sven/linux.git/kernel/user_namespace.c, branch v4.15.6

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

2017-11-16T20:20:15Z

Pull user namespace update from Eric Biederman: "The only change that is production ready this round is the work to increase the number of uid and gid mappings a user namespace can support from 5 to 340. This code was carefully benchmarked and it was confirmed that in the existing cases the performance remains the same. In the worst case with 340 mappings an cache cold stat times go from 158ns to 248ns. That is noticable but still quite small, and only the people who are doing crazy things pay the cost. This work uncovered some documentation and cleanup opportunities in the mapping code, and patches to make those cleanups and improve the documentation will be coming in the next merge window" * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: userns: Simplify insert_extent userns: Make map_id_down a wrapper for map_id_range_down userns: Don't read extents twice in m_start userns: Simplify the user and group mapping functions userns: Don't special case a count of 0 userns: bump idmap limits to 340 userns: use union in {g,u}idmap struct

userns: Simplify insert_extent

2017-10-31T22:23:13Z

Consolidate the code to write to the new mapping at the end of the function to remove the duplication. Move the increase in the number of mappings into insert_extent, keeping the logic together. Just a small increase in readability and maintainability. Signed-off-by: "Eric W. Biederman"

userns: Make map_id_down a wrapper for map_id_range_down

2017-10-31T22:23:13Z

There is no good reason for this code duplication, the number of cache line accesses not the number of instructions are the bottleneck in this code. Therefore simplify maintenance by removing unnecessary code. Signed-off-by: "Eric W. Biederman"

userns: Don't read extents twice in m_start

2017-10-31T22:23:12Z

This is important so reading /proc//{uid_map,gid_map,projid_map} while the map is being written does not do strange things. Signed-off-by: "Eric W. Biederman"

userns: Simplify the user and group mapping functions

2017-10-31T22:23:12Z

Consolidate reading the number of extents and computing the return value in the map_id_down, map_id_range_down and map_id_range. This removal of one read of extents makes one smp_rmb unnecessary and makes the code safe it is executed during the map write. Reading the number of extents twice and depending on the result being the same is not safe, as it could be 0 the first time and > 5 the second time, which would lead to misinterpreting the union fields. The consolidation of the return value just removes a duplicate caluculation which should make it easier to understand and maintain the code. Signed-off-by: "Eric W. Biederman"

userns: Don't special case a count of 0

2017-10-31T22:23:11Z

We can always use a count of 1 so there is no reason to have a special case of a count of 0. Signed-off-by: Eric W. Biederman

userns: bump idmap limits to 340

2017-10-31T22:23:04Z

There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include #include #include #include #include #include #include #include #include #include #include int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner CC: Serge Hallyn CC: Eric Biederman Signed-off-by: Eric W. Biederman

locking/atomics: COCCINELLE/treewide: Convert trivial ACCESS_ONCE() patterns to READ_ONCE()/WRITE_ONCE()

2017-10-25T09:01:08Z

Please do not apply this to mainline directly, instead please re-run the coccinelle script shown below and apply its output. For several reasons, it is desirable to use {READ,WRITE}_ONCE() in preference to ACCESS_ONCE(), and new code is expected to use one of the former. So far, there's been no reason to change most existing uses of ACCESS_ONCE(), as these aren't harmful, and changing them results in churn. However, for some features, the read/write distinction is critical to correct operation. To distinguish these cases, separate read/write accessors must be used. This patch migrates (most) remaining ACCESS_ONCE() instances to {READ,WRITE}_ONCE(), using the following coccinelle script: ---- // Convert trivial ACCESS_ONCE() uses to equivalent READ_ONCE() and // WRITE_ONCE() // $ make coccicheck COCCI=/home/mark/once.cocci SPFLAGS="--include-headers" MODE=patch virtual patch @ depends on patch @ expression E1, E2; @@ - ACCESS_ONCE(E1) = E2 + WRITE_ONCE(E1, E2) @ depends on patch @ expression E; @@ - ACCESS_ONCE(E) + READ_ONCE(E) ---- Signed-off-by: Mark Rutland Signed-off-by: Paul E. McKenney Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: davem@davemloft.net Cc: linux-arch@vger.kernel.org Cc: mpe@ellerman.id.au Cc: shuah@kernel.org Cc: snitzer@redhat.com Cc: thor.thayer@linux.intel.com Cc: tj@kernel.org Cc: viro@zeniv.linux.org.uk Cc: will.deacon@arm.com Link: http://lkml.kernel.org/r/1508792849-3115-19-git-send-email-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar

userns,pidns: Verify the userns for new pid namespaces

2017-07-20T12:43:58Z

It is pointless and confusing to allow a pid namespace hierarchy and the user namespace hierarchy to get out of sync. The owner of a child pid namespace should be the owner of the parent pid namespace or a descendant of the owner of the parent pid namespace. Otherwise it is possible to construct scenarios where a process has a capability over a parent pid namespace but does not have the capability over a child pid namespace. Which confusingly makes permission checks non-transitive. It requires use of setns into a pid namespace (but not into a user namespace) to create such a scenario. Add the function in_userns to help in making this determination. v2: Optimized in_userns by using level as suggested by: Kirill Tkhai Ref: 49f4d8b93ccf ("pidns: Capture the user namespace and filter ns_last_pid") Signed-off-by: "Eric W. Biederman"

sched/headers: Prepare for new header dependencies before moving code to

2017-03-02T07:42:29Z

We are going to split out of , which will have to be picked up from other headers and a couple of .c files. Create a trivial placeholder file that just maps to to make this patch obviously correct and bisectable. Include the new header in the files that are going to need it. Acked-by: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar