user/sven/linux.git, branch v3.2.74

Linux 3.2.74

2015-11-27T12:48:26Z

splice: sendfile() at once fails for big files

2015-11-27T12:48:25Z

commit 0ff28d9f4674d781e492bcff6f32f0fe48cf0fed upstream. Using sendfile with below small program to get MD5 sums of some files, it appear that big files (over 64kbytes with 4k pages system) get a wrong MD5 sum while small files get the correct sum. This program uses sendfile() to send a file to an AF_ALG socket for hashing. /* md5sum2.c */ #include #include #include #include #include #include #include #include #include int main(int argc, char **argv) { int sk = socket(AF_ALG, SOCK_SEQPACKET, 0); struct stat st; struct sockaddr_alg sa = { .salg_family = AF_ALG, .salg_type = "hash", .salg_name = "md5", }; int n; bind(sk, (struct sockaddr*)&sa, sizeof(sa)); for (n = 1; n < argc; n++) { int size; int offset = 0; char buf[4096]; int fd; int sko; int i; fd = open(argv[n], O_RDONLY); sko = accept(sk, NULL, 0); fstat(fd, &st); size = st.st_size; sendfile(sko, fd, &offset, size); size = read(sko, buf, sizeof(buf)); for (i = 0; i < size; i++) printf("%2.2x", buf[i]); printf(" %s\n", argv[n]); close(fd); close(sko); } exit(0); } Test below is done using official linux patch files. First result is with a software based md5sum. Second result is with the program above. root@vgoip:~# ls -l patch-3.6.* -rw-r--r-- 1 root root 64011 Aug 24 12:01 patch-3.6.2.gz -rw-r--r-- 1 root root 94131 Aug 24 12:01 patch-3.6.3.gz root@vgoip:~# md5sum patch-3.6.* b3ffb9848196846f31b2ff133d2d6443 patch-3.6.2.gz c5e8f687878457db77cb7158c38a7e43 patch-3.6.3.gz root@vgoip:~# ./md5sum2 patch-3.6.* b3ffb9848196846f31b2ff133d2d6443 patch-3.6.2.gz 5fd77b24e68bb24dcc72d6e57c64790e patch-3.6.3.gz After investivation, it appears that sendfile() sends the files by blocks of 64kbytes (16 times PAGE_SIZE). The problem is that at the end of each block, the SPLICE_F_MORE flag is missing, therefore the hashing operation is reset as if it was the end of the file. This patch adds SPLICE_F_MORE to the flags when more data is pending. With the patch applied, we get the correct sums: root@vgoip:~# md5sum patch-3.6.* b3ffb9848196846f31b2ff133d2d6443 patch-3.6.2.gz c5e8f687878457db77cb7158c38a7e43 patch-3.6.3.gz root@vgoip:~# ./md5sum2 patch-3.6.* b3ffb9848196846f31b2ff133d2d6443 patch-3.6.2.gz c5e8f687878457db77cb7158c38a7e43 patch-3.6.3.gz Signed-off-by: Christophe Leroy Signed-off-by: Jens Axboe Signed-off-by: Ben Hutchings

net: avoid NULL deref in inet_ctl_sock_destroy()

2015-11-27T12:48:25Z

[ Upstream commit 8fa677d2706d325d71dab91bf6e6512c05214e37 ] Under low memory conditions, tcp_sk_init() and icmp_sk_init() can both iterate on all possible cpus and call inet_ctl_sock_destroy(), with eventual NULL pointer. Signed-off-by: Eric Dumazet Reported-by: Dmitry Vyukov Signed-off-by: David S. Miller Signed-off-by: Ben Hutchings

ipmr: fix possible race resulting from improper usage of IP_INC_STATS_BH() in preemptible context.

2015-11-27T12:48:25Z

[ Upstream commit 44f49dd8b5a606870a1f21101522a0f9c4414784 ] Fixes the following kernel BUG : BUG: using __this_cpu_add() in preemptible [00000000] code: bash/2758 caller is __this_cpu_preempt_check+0x13/0x15 CPU: 0 PID: 2758 Comm: bash Tainted: P O 3.18.19 #2 ffffffff8170eaca ffff880110d1b788 ffffffff81482b2a 0000000000000000 0000000000000000 ffff880110d1b7b8 ffffffff812010ae ffff880007cab800 ffff88001a060800 ffff88013a899108 ffff880108b84240 ffff880110d1b7c8 Call Trace: [] dump_stack+0x52/0x80 [] check_preemption_disabled+0xce/0xe1 [] __this_cpu_preempt_check+0x13/0x15 [] ipmr_queue_xmit+0x647/0x70c [] ip_mr_forward+0x32f/0x34e [] ip_mroute_setsockopt+0xe03/0x108c [] ? get_parent_ip+0x11/0x42 [] ? pollwake+0x4d/0x51 [] ? default_wake_function+0x0/0xf [] ? get_parent_ip+0x11/0x42 [] ? __wake_up_common+0x45/0x77 [] ? _raw_spin_unlock_irqrestore+0x1d/0x32 [] ? __wake_up_sync_key+0x4a/0x53 [] ? sock_def_readable+0x71/0x75 [] do_ip_setsockopt+0x9d/0xb55 [] ? unix_seqpacket_sendmsg+0x3f/0x41 [] ? sock_sendmsg+0x6d/0x86 [] ? sockfd_lookup_light+0x12/0x5d [] ? SyS_sendto+0xf3/0x11b [] ? new_sync_read+0x82/0xaa [] compat_ip_setsockopt+0x3b/0x99 [] compat_raw_setsockopt+0x11/0x32 [] compat_sock_common_setsockopt+0x18/0x1f [] compat_SyS_setsockopt+0x1a9/0x1cf [] compat_SyS_socketcall+0x180/0x1e3 [] cstar_dispatch+0x7/0x1e Signed-off-by: Ani Sinha Acked-by: Eric Dumazet Signed-off-by: David S. Miller [bwh: Backported to 3.2: ipmr doesn't implement IPSTATS_MIB_OUTOCTETS] Signed-off-by: Ben Hutchings

RDS-TCP: Recover correctly from pskb_pull()/pksb_trim() failure in rds_tcp_data_recv

2015-11-27T12:48:25Z

[ Upstream commit 8ce675ff39b9958d1c10f86cf58e357efaafc856 ] Either of pskb_pull() or pskb_trim() may fail under low memory conditions. If rds_tcp_data_recv() ignores such failures, the application will receive corrupted data because the skb has not been correctly carved to the RDS datagram size. Avoid this by handling pskb_pull/pskb_trim failure in the same manner as the skb_clone failure: bail out of rds_tcp_data_recv(), and retry via the deferred call to rds_send_worker() that gets set up on ENOMEM from rds_tcp_read_sock() Signed-off-by: Sowmini Varadhan Acked-by: Santosh Shilimkar Signed-off-by: David S. Miller Signed-off-by: Ben Hutchings

irda: precedence bug in irlmp_seq_hb_idx()

2015-11-27T12:48:25Z

[ Upstream commit 50010c20597d14667eff0fdb628309986f195230 ] This is decrementing the pointer, instead of the value stored in the pointer. KASan detects it as an out of bounds reference. Reported-by: "Berry Cheng 程君(成淼)" Signed-off-by: Dan Carpenter Signed-off-by: David S. Miller Signed-off-by: Ben Hutchings

fs: if a coredump already exists, unlink and recreate with O_EXCL

2015-11-27T12:48:25Z

commit fbb1816942c04429e85dbf4c1a080accc534299e upstream. It was possible for an attacking user to trick root (or another user) into writing his coredumps into an attacker-readable, pre-existing file using rename() or link(), causing the disclosure of secret data from the victim process' virtual memory. Depending on the configuration, it was also possible to trick root into overwriting system files with coredumps. Fix that issue by never writing coredumps into existing files. Requirements for the attack: - The attack only applies if the victim's process has a nonzero RLIMIT_CORE and is dumpable. - The attacker can trick the victim into coredumping into an attacker-writable directory D, either because the core_pattern is relative and the victim's cwd is attacker-writable or because an absolute core_pattern pointing to a world-writable directory is used. - The attacker has one of these: A: on a system with protected_hardlinks=0: execute access to a folder containing a victim-owned, attacker-readable file on the same partition as D, and the victim-owned file will be deleted before the main part of the attack takes place. (In practice, there are lots of files that fulfill this condition, e.g. entries in Debian's /var/lib/dpkg/info/.) This does not apply to most Linux systems because most distros set protected_hardlinks=1. B: on a system with protected_hardlinks=1: execute access to a folder containing a victim-owned, attacker-readable and attacker-writable file on the same partition as D, and the victim-owned file will be deleted before the main part of the attack takes place. (This seems to be uncommon.) C: on any system, independent of protected_hardlinks: write access to a non-sticky folder containing a victim-owned, attacker-readable file on the same partition as D (This seems to be uncommon.) The basic idea is that the attacker moves the victim-owned file to where he expects the victim process to dump its core. The victim process dumps its core into the existing file, and the attacker reads the coredump from it. If the attacker can't move the file because he does not have write access to the containing directory, he can instead link the file to a directory he controls, then wait for the original link to the file to be deleted (because the kernel checks that the link count of the corefile is 1). A less reliable variant that requires D to be non-sticky works with link() and does not require deletion of the original link: link() the file into D, but then unlink() it directly before the kernel performs the link count check. On systems with protected_hardlinks=0, this variant allows an attacker to not only gain information from coredumps, but also clobber existing, victim-writable files with coredumps. (This could theoretically lead to a privilege escalation.) Signed-off-by: Jann Horn Cc: Kees Cook Cc: Al Viro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds [bwh: Backported to 3.2: adjust filename, context] Signed-off-by: Ben Hutchings

fs: make dumpable=2 require fully qualified path

2015-11-27T12:48:24Z

commit 9520628e8ceb69fa9a4aee6b57f22675d9e1b709 upstream. When the suid_dumpable sysctl is set to "2", and there is no core dump pipe defined in the core_pattern sysctl, a local user can cause core files to be written to root-writable directories, potentially with user-controlled content. This means an admin can unknowningly reintroduce a variation of CVE-2006-2451, allowing local users to gain root privileges. $ cat /proc/sys/fs/suid_dumpable 2 $ cat /proc/sys/kernel/core_pattern core $ ulimit -c unlimited $ cd / $ ls -l core ls: cannot access core: No such file or directory $ touch core touch: cannot touch `core': Permission denied $ OHAI="evil-string-here" ping localhost >/dev/null 2>&1 & $ pid=$! $ sleep 1 $ kill -SEGV $pid $ ls -l core -rw------- 1 root kees 458752 Jun 21 11:35 core $ sudo strings core | grep evil OHAI=evil-string-here While cron has been fixed to abort reading a file when there is any parse error, there are still other sensitive directories that will read any file present and skip unparsable lines. Instead of introducing a suid_dumpable=3 mode and breaking all users of mode 2, this only disables the unsafe portion of mode 2 (writing to disk via relative path). Most users of mode 2 (e.g. Chrome OS) already use a core dump pipe handler, so this change will not break them. For the situations where a pipe handler is not defined but mode 2 is still active, crash dumps will only be written to fully qualified paths. If a relative path is defined (e.g. the default "core" pattern), dump attempts will trigger a printk yelling about the lack of a fully qualified path. Signed-off-by: Kees Cook Cc: Alexander Viro Cc: Alan Cox Cc: "Eric W. Biederman" Cc: Doug Ledford Cc: Serge Hallyn Cc: James Morris Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings Reviewed-by: James Morris

binfmt_elf: Don't clobber passed executable's file header

2015-11-27T12:48:24Z

commit b582ef5c53040c5feef4c96a8f9585b6831e2441 upstream. Do not clobber the buffer space passed from `search_binary_handler' and originally preloaded by `prepare_binprm' with the executable's file header by overwriting it with its interpreter's file header. Instead keep the buffer space intact and directly use the data structure locally allocated for the interpreter's file header, fixing a bug introduced in 2.1.14 with loadable module support (linux-mips.org commit beb11695 [Import of Linux/MIPS 2.1.14], predating kernel.org repo's history). Adjust the amount of data read from the interpreter's file accordingly. This was not an issue before loadable module support, because back then `load_elf_binary' was executed only once for a given ELF executable, whether the function succeeded or failed. With loadable module support supported and enabled, upon a failure of `load_elf_binary' -- which may for example be caused by architecture code rejecting an executable due to a missing hardware feature requested in the file header -- a module load is attempted and then the function reexecuted by `search_binary_handler'. With the executable's file header replaced with its interpreter's file header the executable can then be erroneously accepted in this subsequent attempt. Signed-off-by: Maciej W. Rozycki Signed-off-by: Al Viro Signed-off-by: Ben Hutchings

FS-Cache: Handle a write to the page immediately beyond the EOF marker

2015-11-27T12:48:24Z

commit 102f4d900c9c8f5ed89ae4746d493fe3ebd7ba64 upstream. Handle a write being requested to the page immediately beyond the EOF marker on a cache object. Currently this gets an assertion failure in CacheFiles because the EOF marker is used there to encode information about a partial page at the EOF - which could lead to an unknown blank spot in the file if we extend the file over it. The problem is actually in fscache where we check the index of the page being written against store_limit. store_limit is set to the number of pages that we're allowed to store by fscache_set_store_limit() - which means it's one more than the index of the last page we're allowed to store. The problem is that we permit writing to a page with an index _equal_ to the store limit - when we should reject that case. Whilst we're at it, change the triggered assertion in CacheFiles to just return -ENOBUFS instead. The assertion failure looks something like this: CacheFiles: Assertion failed 1000 < 7b1 is false ------------[ cut here ]------------ kernel BUG at fs/cachefiles/rdwr.c:962! ... RIP: 0010:[] [] cachefiles_write_page+0x273/0x2d0 [cachefiles] Signed-off-by: David Howells Signed-off-by: Al Viro [bwh: Backported to 3.2: we don't have __kernel_write() so keep using the open-coded equivalent] Signed-off-by: Ben Hutchings