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author | Christophe Leroy <christophe.leroy@csgroup.eu> | 2022-01-14 14:05:13 -0800 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2022-01-15 16:30:26 +0200 |
commit | 677b2a8c1f25db5b09c1ef5bf72faa39ea81d9cf (patch) | |
tree | 663d5a0a7a5fade5b9edaeb0c7ef16fd320b0d23 | |
parent | 43b93121056c524e2af77d561900ea856d32029c (diff) | |
download | linux-677b2a8c1f25db5b09c1ef5bf72faa39ea81d9cf.tar.gz linux-677b2a8c1f25db5b09c1ef5bf72faa39ea81d9cf.tar.bz2 linux-677b2a8c1f25db5b09c1ef5bf72faa39ea81d9cf.zip |
gup: avoid multiple user access locking/unlocking in fault_in_{read/write}able
fault_in_readable() and fault_in_writeable() perform __get_user() and
__put_user() in a loop, implying multiple user access locking/unlocking.
To avoid that, use user access blocks.
Link: https://lkml.kernel.org/r/720dcf79314acca1a78fae56d478cc851952149d.1637084492.git.christophe.leroy@csgroup.eu
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r-- | mm/gup.c | 18 |
1 files changed, 10 insertions, 8 deletions
@@ -1672,21 +1672,22 @@ size_t fault_in_writeable(char __user *uaddr, size_t size) if (unlikely(size == 0)) return 0; + if (!user_write_access_begin(uaddr, size)) + return size; if (!PAGE_ALIGNED(uaddr)) { - if (unlikely(__put_user(0, uaddr) != 0)) - return size; + unsafe_put_user(0, uaddr, out); uaddr = (char __user *)PAGE_ALIGN((unsigned long)uaddr); } end = (char __user *)PAGE_ALIGN((unsigned long)start + size); if (unlikely(end < start)) end = NULL; while (uaddr != end) { - if (unlikely(__put_user(0, uaddr) != 0)) - goto out; + unsafe_put_user(0, uaddr, out); uaddr += PAGE_SIZE; } out: + user_write_access_end(); if (size > uaddr - start) return size - (uaddr - start); return 0; @@ -1771,21 +1772,22 @@ size_t fault_in_readable(const char __user *uaddr, size_t size) if (unlikely(size == 0)) return 0; + if (!user_read_access_begin(uaddr, size)) + return size; if (!PAGE_ALIGNED(uaddr)) { - if (unlikely(__get_user(c, uaddr) != 0)) - return size; + unsafe_get_user(c, uaddr, out); uaddr = (const char __user *)PAGE_ALIGN((unsigned long)uaddr); } end = (const char __user *)PAGE_ALIGN((unsigned long)start + size); if (unlikely(end < start)) end = NULL; while (uaddr != end) { - if (unlikely(__get_user(c, uaddr) != 0)) - goto out; + unsafe_get_user(c, uaddr, out); uaddr += PAGE_SIZE; } out: + user_read_access_end(); (void)c; if (size > uaddr - start) return size - (uaddr - start); |